diff --git a/hapi/distributed.py b/hapi/distributed.py
index 39bf9a35e79792a1f0c9dd23d296730fdc31daf5..5460cd435f3ebb67cdfeff4188fe2b22d179c277 100644
--- a/hapi/distributed.py
+++ b/hapi/distributed.py
@@ -48,6 +48,35 @@ class DistributedBatchSampler(BatchSampler):
             batch indices. Default False.
         drop_last(bool): whether drop the last incomplete batch dataset size
             is not divisible by the batch size. Default False
+
+    Examples:
+        .. code-block:: python
+
+            import numpy as np
+
+            from hapi.datasets import MNIST
+            from hapi.distributed import DistributedBatchSampler
+
+            class MnistDataset(MNIST):
+                def __init__(self, mode, return_label=True):
+                    super(MnistDataset, self).__init__(mode=mode)
+                    self.return_label = return_label
+
+                def __getitem__(self, idx):
+                    img = np.reshape(self.images[idx], [1, 28, 28])
+                    if self.return_label:
+                        return img, np.array(self.labels[idx]).astype('int64')
+                    return img,
+
+                def __len__(self):
+                    return len(self.images)
+
+            train_dataset = MnistDataset(mode='train')
+            dist_train_dataloader = DistributedBatchSampler(train_dataset, batch_size=64)
+
+            for data in dist_train_dataloader:
+                # do something
+                break
     """
 
     def __init__(self, dataset, batch_size, shuffle=False, drop_last=False):
diff --git a/hapi/download.py b/hapi/download.py
index 58c60c3885950aa0799b67a6824c3ca188e0840a..cfd31664dec5b38382e7b32aa41ab4f50fbe5480 100644
--- a/hapi/download.py
+++ b/hapi/download.py
@@ -55,6 +55,15 @@ def get_weights_path_from_url(url, md5sum=None):
     
     Returns:
         str: a local path to save downloaded weights.
+
+    Examples:
+        .. code-block:: python
+
+            from hapi.download import get_weights_path_from_url
+
+            resnet18_pretrained_weight_url = 'https://paddle-hapi.bj.bcebos.com/models/resnet18.pdparams'
+            local_weight_path = get_weights_path_from_url(resnet18_pretrained_weight_url)
+
     """
     path = get_path_from_url(url, WEIGHTS_HOME, md5sum)
     return path
diff --git a/hapi/logger.py b/hapi/logger.py
index 83e8a35e5da0ea6a80705778ddf41a73f26b80e5..54313639e9f959ba1c9a0db1e8044bd7515153f4 100644
--- a/hapi/logger.py
+++ b/hapi/logger.py
@@ -38,7 +38,7 @@ def setup_logger(output=None, name="hapi", log_level=logging.INFO):
 
     # stdout logging: only local rank==0
     local_rank = ParallelEnv().local_rank
-    if local_rank == 0:
+    if local_rank == 0 and not logger.hasHandlers():
         ch = logging.StreamHandler(stream=sys.stdout)
         ch.setLevel(log_level)
 
diff --git a/hapi/loss.py b/hapi/loss.py
index 7abddf22f1519b6bd1a649f663b22f315366ca7a..9bdf04af4e356c9e2312ba28e0627f38355b00c3 100644
--- a/hapi/loss.py
+++ b/hapi/loss.py
@@ -30,8 +30,8 @@ class Loss(object):
     Base class for loss, encapsulates loss logic and APIs
 
     Usage:
-    custom_loss = CustomLoss()
-    loss = custom_loss(inputs, labels)
+        custom_loss = CustomLoss()
+        loss = custom_loss(inputs, labels)
     """
 
     def __init__(self, average=True):
@@ -63,10 +63,25 @@ class CrossEntropy(Loss):
         average (bool, optional): Indicate whether to average the loss, Default: True.
     Returns:
         list[Variable]: The tensor variable storing the cross_entropy_loss of inputs and labels.
+
+    Examples:
+        .. code-block:: python
+
+            from hapi.model import Input
+            from hapi.vision.models import LeNet
+            from hapi.loss import CrossEntropy
+
+            inputs = [Input([-1, 1, 28, 28], 'float32', name='image')]
+            labels = [Input([None, 1], 'int64', name='label')]
+
+            model = LeNet()
+            loss = CrossEntropy()
+            model.prepare(loss_function=loss, inputs=inputs, labels=labels)
+            
     """
 
     def __init__(self, average=True):
-        super(CrossEntropy, self).__init__()
+        super(CrossEntropy, self).__init__(average)
 
     def forward(self, outputs, labels):
         return [
@@ -85,10 +100,24 @@ class SoftmaxWithCrossEntropy(Loss):
         average (bool, optional): Indicate whether to average the loss, Default: True.
     Returns:
         list[Variable]: The tensor variable storing the cross_entropy_loss of inputs and labels.
+
+    Examples:
+        .. code-block:: python
+
+            from hapi.model import Input
+            from hapi.vision.models import LeNet
+            from hapi.loss import SoftmaxWithCrossEntropy
+
+            inputs = [Input([-1, 1, 28, 28], 'float32', name='image')]
+            labels = [Input([None, 1], 'int64', name='label')]
+
+            model = LeNet(classifier_activation=None)
+            loss = SoftmaxWithCrossEntropy()
+            model.prepare(loss_function=loss, inputs=inputs, labels=labels)
     """
 
     def __init__(self, average=True):
-        super(SoftmaxWithCrossEntropy, self).__init__()
+        super(SoftmaxWithCrossEntropy, self).__init__(average)
 
     def forward(self, outputs, labels):
         return [
diff --git a/hapi/vision/models/darknet.py b/hapi/vision/models/darknet.py
index 582b4c56cee3f8aeb450db54f3a6551dc8a04689..993d0ca6b70aa90d7599967f5654c71055bd1f15 100755
--- a/hapi/vision/models/darknet.py
+++ b/hapi/vision/models/darknet.py
@@ -144,6 +144,13 @@ class DarkNet(Model):
                             will not be defined. Default: 1000.
         with_pool (bool): use pool before the last fc layer or not. Default: True.
         classifier_activation (str): activation for the last fc layer. Default: 'softmax'.
+
+    Examples:
+        .. code-block:: python
+
+            from hapi.vision.models import DarkNet
+
+            model = DarkNet()
     """
 
     def __init__(self,
@@ -233,5 +240,17 @@ def darknet53(pretrained=False, **kwargs):
         input_channels (bool): channel number of input data, default 3. 
         pretrained (bool): If True, returns a model pre-trained on ImageNet,
             default True.
+
+    Examples:
+        .. code-block:: python
+
+            from hapi.vision.models import darknet53
+
+            # build model
+            model = darknet53()
+
+            #build model and load imagenet pretrained weight
+            model = darknet53(pretrained=True)
+            
     """
     return _darknet('darknet53', 53, pretrained, **kwargs)
diff --git a/hapi/vision/models/lenet.py b/hapi/vision/models/lenet.py
index 0f88bc91cb130f1432ecf29e6aae10755be1392d..568165490e5daaafc921f32553000b4eda558f85 100644
--- a/hapi/vision/models/lenet.py
+++ b/hapi/vision/models/lenet.py
@@ -29,6 +29,13 @@ class LeNet(Model):
         num_classes (int): output dim of last fc layer. If num_classes <=0, last fc layer 
                             will not be defined. Default: 10.
         classifier_activation (str): activation for the last fc layer. Default: 'softmax'.
+
+    Examples:
+        .. code-block:: python
+
+            from hapi.vision.models import LeNet
+
+            model = LeNet()
     """
 
     def __init__(self, num_classes=10, classifier_activation='softmax'):
diff --git a/hapi/vision/models/mobilenetv1.py b/hapi/vision/models/mobilenetv1.py
index b725afac14c25c70008a5ef3167e0b18f3f9b521..8afd53a2e2dce9d7e93a6bee9bce8c71668dc3fb 100644
--- a/hapi/vision/models/mobilenetv1.py
+++ b/hapi/vision/models/mobilenetv1.py
@@ -115,6 +115,13 @@ class MobileNetV1(Model):
                             will not be defined. Default: 1000.
         with_pool (bool): use pool before the last fc layer or not. Default: True.
         classifier_activation (str): activation for the last fc layer. Default: 'softmax'.
+
+    Examples:
+        .. code-block:: python
+
+            from hapi.vision.models import MobileNetV1
+
+            model = MobileNetV1()
     """
 
     def __init__(self,
@@ -282,6 +289,20 @@ def mobilenet_v1(pretrained=False, scale=1.0, **kwargs):
     Args:
         pretrained (bool): If True, returns a model pre-trained on ImageNet. Default: False.
         scale: (float): scale of channels in each layer. Default: 1.0.
+
+    Examples:
+        .. code-block:: python
+
+            from hapi.vision.models import mobilenet_v1
+
+            # build model
+            model = mobilenet_v1()
+
+            #build model and load imagenet pretrained weight
+            model = mobilenet_v1(pretrained=True)
+
+            #build mobilenet v1 with scale=0.5
+            model = mobilenet_v1(scale=0.5)
     """
     model = _mobilenet(
         'mobilenetv1_' + str(scale), pretrained, scale=scale, **kwargs)
diff --git a/hapi/vision/models/mobilenetv2.py b/hapi/vision/models/mobilenetv2.py
index c9591b22a505d3bd7a60c12597919bda182f88b5..0b0179334a48fe67dd2e7f9cca3625932ffb33b2 100644
--- a/hapi/vision/models/mobilenetv2.py
+++ b/hapi/vision/models/mobilenetv2.py
@@ -160,6 +160,13 @@ class MobileNetV2(Model):
                             will not be defined. Default: 1000.
         with_pool (bool): use pool before the last fc layer or not. Default: True.
         classifier_activation (str): activation for the last fc layer. Default: 'softmax'.
+
+    Examples:
+        .. code-block:: python
+
+            from hapi.vision.models import MobileNetV2
+
+            model = MobileNetV2()
     """
 
     def __init__(self,
@@ -256,6 +263,20 @@ def mobilenet_v2(pretrained=False, scale=1.0, **kwargs):
     Args:
         pretrained (bool): If True, returns a model pre-trained on ImageNet. Default: False.
         scale: (float): scale of channels in each layer. Default: 1.0.
+
+    Examples:
+        .. code-block:: python
+
+            from hapi.vision.models import mobilenet_v2
+
+            # build model
+            model = mobilenet_v2()
+
+            #build model and load imagenet pretrained weight
+            model = mobilenet_v2(pretrained=True)
+
+            #build mobilenet v2 with scale=0.5
+            model = mobilenet_v2(scale=0.5)
     """
     model = _mobilenet(
         'mobilenetv2_' + str(scale), pretrained, scale=scale, **kwargs)
diff --git a/hapi/vision/models/resnet.py b/hapi/vision/models/resnet.py
index 1adb085c7d0e26fb89a036303812a537d028cf3f..1f3c93add19cc4962b8fe68ccf9502d6adb69086 100644
--- a/hapi/vision/models/resnet.py
+++ b/hapi/vision/models/resnet.py
@@ -26,7 +26,8 @@ from hapi.model import Model
 from hapi.download import get_weights_path_from_url
 
 __all__ = [
-    'ResNet', 'resnet18', 'resnet34', 'resnet50', 'resnet101', 'resnet152'
+    'ResNet', 'resnet18', 'resnet34', 'resnet50', 'resnet101', 'resnet152',
+    'BottleneckBlock', 'BasicBlock'
 ]
 
 model_urls = {
@@ -75,7 +76,8 @@ class ConvBNLayer(fluid.dygraph.Layer):
 
 
 class BasicBlock(fluid.dygraph.Layer):
-
+    """residual block of resnet18 and resnet34
+    """
     expansion = 1
 
     def __init__(self, num_channels, num_filters, stride, shortcut=True):
@@ -117,6 +119,8 @@ class BasicBlock(fluid.dygraph.Layer):
 
 
 class BottleneckBlock(fluid.dygraph.Layer):
+    """residual block of resnet50, resnet101 amd resnet152
+    """
 
     expansion = 4
 
@@ -177,6 +181,16 @@ class ResNet(Model):
                             will not be defined. Default: 1000.
         with_pool (bool): use pool before the last fc layer or not. Default: True.
         classifier_activation (str): activation for the last fc layer. Default: 'softmax'.
+
+    Examples:
+        .. code-block:: python
+
+            from hapi.vision.models import ResNet, BottleneckBlock, BasicBlock
+
+            resnet50 = ResNet(BottleneckBlock, 50)
+
+            resnet18 = ResNet(BasicBlock, 18)
+
     """
 
     def __init__(self,
@@ -280,6 +294,17 @@ def resnet18(pretrained=False, **kwargs):
     
     Args:
         pretrained (bool): If True, returns a model pre-trained on ImageNet
+
+    Examples:
+        .. code-block:: python
+
+            from hapi.vision.models import resnet18
+
+            # build model
+            model = resnet18()
+
+            #build model and load imagenet pretrained weight
+            model = resnet18(pretrained=True)
     """
     return _resnet('resnet18', BasicBlock, 18, pretrained, **kwargs)
 
@@ -289,6 +314,17 @@ def resnet34(pretrained=False, **kwargs):
     
     Args:
         pretrained (bool): If True, returns a model pre-trained on ImageNet
+    
+    Examples:
+        .. code-block:: python
+
+            from hapi.vision.models import resnet34
+
+            # build model
+            model = resnet34()
+
+            #build model and load imagenet pretrained weight
+            model = resnet34(pretrained=True)
     """
     return _resnet('resnet34', BasicBlock, 34, pretrained, **kwargs)
 
@@ -298,6 +334,17 @@ def resnet50(pretrained=False, **kwargs):
     
     Args:
         pretrained (bool): If True, returns a model pre-trained on ImageNet
+
+    Examples:
+        .. code-block:: python
+
+            from hapi.vision.models import resnet50
+
+            # build model
+            model = resnet50()
+
+            #build model and load imagenet pretrained weight
+            model = resnet50(pretrained=True)
     """
     return _resnet('resnet50', BottleneckBlock, 50, pretrained, **kwargs)
 
@@ -307,6 +354,17 @@ def resnet101(pretrained=False, **kwargs):
     
     Args:
         pretrained (bool): If True, returns a model pre-trained on ImageNet
+
+    Examples:
+        .. code-block:: python
+
+            from hapi.vision.models import resnet101
+
+            # build model
+            model = resnet101()
+
+            #build model and load imagenet pretrained weight
+            model = resnet101(pretrained=True)
     """
     return _resnet('resnet101', BottleneckBlock, 101, pretrained, **kwargs)
 
@@ -316,5 +374,16 @@ def resnet152(pretrained=False, **kwargs):
     
     Args:
         pretrained (bool): If True, returns a model pre-trained on ImageNet
+
+    Examples:
+        .. code-block:: python
+
+            from hapi.vision.models import resnet152
+
+            # build model
+            model = resnet152()
+
+            #build model and load imagenet pretrained weight
+            model = resnet152(pretrained=True)
     """
     return _resnet('resnet152', BottleneckBlock, 152, pretrained, **kwargs)
diff --git a/hapi/vision/models/vgg.py b/hapi/vision/models/vgg.py
index 0cd7cb79e514873991382b7a577b2b2a8d204fba..3a8c59737ab4d42f72de27d20846bb13d727a6ac 100644
--- a/hapi/vision/models/vgg.py
+++ b/hapi/vision/models/vgg.py
@@ -143,6 +143,17 @@ def vgg11(pretrained=False, batch_norm=False, **kwargs):
     Args:
         pretrained (bool): If True, returns a model pre-trained on ImageNet. Default: False.
         batch_norm (bool): If True, returns a model with batch_norm layer. Default: False.
+
+    Examples:
+        .. code-block:: python
+
+            from hapi.vision.models import vgg11
+
+            # build model
+            model = vgg11()
+
+            #build vgg11 model with batch_norm
+            model = vgg11(batch_norm=True)
     """
     model_name = 'vgg11'
     if batch_norm:
@@ -156,6 +167,17 @@ def vgg13(pretrained=False, batch_norm=False, **kwargs):
     Args:
         pretrained (bool): If True, returns a model pre-trained on ImageNet. Default: False.
         batch_norm (bool): If True, returns a model with batch_norm layer. Default: False.
+
+    Examples:
+        .. code-block:: python
+
+            from hapi.vision.models import vgg13
+
+            # build model
+            model = vgg13()
+
+            #build vgg13 model with batch_norm
+            model = vgg13(batch_norm=True)
     """
     model_name = 'vgg13'
     if batch_norm:
@@ -169,6 +191,17 @@ def vgg16(pretrained=False, batch_norm=False, **kwargs):
     Args:
         pretrained (bool): If True, returns a model pre-trained on ImageNet. Default: False.
         batch_norm (bool): If True, returns a model with batch_norm layer. Default: False.
+
+    Examples:
+        .. code-block:: python
+
+            from hapi.vision.models import vgg16
+
+            # build model
+            model = vgg16()
+
+            #build vgg16 model with batch_norm
+            model = vgg16(batch_norm=True)
     """
     model_name = 'vgg16'
     if batch_norm:
@@ -182,6 +215,17 @@ def vgg19(pretrained=False, batch_norm=False, **kwargs):
     Args:
         pretrained (bool): If True, returns a model pre-trained on ImageNet. Default: False.
         batch_norm (bool): If True, returns a model with batch_norm layer. Default: False.
+
+    Examples:
+        .. code-block:: python
+
+            from hapi.vision.models import vgg19
+
+            # build model
+            model = vgg19()
+
+            #build vgg19 model with batch_norm
+            model = vgg19(batch_norm=True)
     """
     model_name = 'vgg19'
     if batch_norm:
diff --git a/hapi/vision/transforms/functional.py b/hapi/vision/transforms/functional.py
index a4ca466c12ca5bf1e4db6fa4e47f58f95f73aea9..2bc3fba7270a935047af9e8710089d921f65d041 100644
--- a/hapi/vision/transforms/functional.py
+++ b/hapi/vision/transforms/functional.py
@@ -39,6 +39,23 @@ def flip(image, code):
             -1 : Flip horizontally and vertically
             0 : Flip vertically
             1 : Flip horizontally
+
+    Examples:
+        .. code-block:: python
+
+            import numpy as np
+            from hapi.vision.transforms import functional as F
+
+            fake_img = np.random.rand(224, 224, 3)
+
+            # flip horizontally and vertically
+            F.flip(fake_img, -1)
+
+            # flip vertically
+            F.flip(fake_img, 0)
+
+            # flip horizontally
+            F.flip(fake_img, 1)
     """
     return cv2.flip(image, flipCode=code)
 
@@ -51,6 +68,18 @@ def resize(img, size, interpolation=cv2.INTER_LINEAR):
         input: Input data, could be image or masks, with (H, W, C) shape
         size: Target size of input data, with (height, width) shape.
         interpolation: Interpolation method.
+
+    Examples:
+        .. code-block:: python
+
+            import numpy as np
+            from hapi.vision.transforms import functional as F
+
+            fake_img = np.random.rand(256, 256, 3)
+
+            F.resize(fake_img, 224)
+
+            F.resize(fake_img, (200, 150))
     """
 
     if isinstance(interpolation, Sequence):
diff --git a/hapi/vision/transforms/transforms.py b/hapi/vision/transforms/transforms.py
index b71b2571bafa23ae3ef58ec943d4e147749332f7..a6c5007441b8db270e38f1b28fa97ac225ed074d 100644
--- a/hapi/vision/transforms/transforms.py
+++ b/hapi/vision/transforms/transforms.py
@@ -118,6 +118,67 @@ class BatchCompose(object):
         transforms (list of ``Transform`` objects): list of transforms to compose.
                                             these transforms perform on batch data.
 
+    Examples:
+    
+        .. code-block:: python
+
+            import numpy as np
+            from paddle.io import DataLoader
+
+            from hapi.model import set_device
+            from hapi.datasets import Flowers
+            from hapi.vision.transforms import Compose, BatchCompose, Resize
+
+            class NormalizeBatch(object):
+                def __init__(self,
+                            mean=[0.485, 0.456, 0.406],
+                            std=[0.229, 0.224, 0.225],
+                            scale=True,
+                            channel_first=True):
+
+                    self.mean = mean
+                    self.std = std
+                    self.scale = scale
+                    self.channel_first = channel_first
+                    if not (isinstance(self.mean, list) and isinstance(self.std, list) and
+                            isinstance(self.scale, bool)):
+                        raise TypeError("{}: input type is invalid.".format(self))
+                    from functools import reduce
+                    if reduce(lambda x, y: x * y, self.std) == 0:
+                        raise ValueError('{}: std is invalid!'.format(self))
+
+                def __call__(self, samples):
+                    for i in range(len(samples)):
+                        samples[i] = list(samples[i])
+                        im = samples[i][0]
+                        im = im.astype(np.float32, copy=False)
+                        mean = np.array(self.mean)[np.newaxis, np.newaxis, :]
+                        std = np.array(self.std)[np.newaxis, np.newaxis, :]
+                        if self.scale:
+                            im = im / 255.0
+                        im -= mean
+                        im /= std
+                        if self.channel_first:
+                            im = im.transpose((2, 0, 1))
+                        samples[i][0] = im
+                    return samples
+
+            transform = Compose([Resize((500, 500))])
+            flowers_dataset = Flowers(mode='test', transform=transform)
+
+            device = set_device('cpu')
+
+            collate_fn = BatchCompose([NormalizeBatch()])
+            loader = DataLoader(
+                        flowers_dataset,
+                        batch_size=4,
+                        places=device,
+                        return_list=True,
+                        collate_fn=collate_fn)
+
+            for data in loader:
+                # do something
+                break
     """
 
     def __init__(self, transforms=[]):
@@ -149,6 +210,20 @@ class Resize(object):
             i.e, if height > width, then image will be rescaled to
             (size * height / width, size)
         interpolation (int): interpolation mode of resize. Default: cv2.INTER_LINEAR.
+
+    Examples:
+    
+        .. code-block:: python
+
+            from hapi.datasets import Flowers
+            from hapi.vision.transforms import Compose, Resize
+
+            transform = Compose([Resize(size=224)])
+            flowers = Flowers(mode='test', transform=transform)
+
+            for i in range(10):
+                sample = flowers[i]
+                print(sample[0].shape, sample[1])
     """
 
     def __init__(self, size, interpolation=cv2.INTER_LINEAR):
@@ -171,6 +246,20 @@ class RandomResizedCrop(object):
         output_size (int|list|tuple): Target size of output image, with (height, width) shape.
         scale (list|tuple): Range of size of the origin size cropped. Default: (0.08, 1.0)
         ratio (list|tuple): Range of aspect ratio of the origin aspect ratio cropped. Default: (0.75, 1.33)
+
+    Examples:
+    
+        .. code-block:: python
+
+            from hapi.datasets import Flowers
+            from hapi.vision.transforms import Compose, Resize, RandomResizedCrop
+
+            transform = Compose([Resize(500), RandomResizedCrop(224)])
+            flowers = Flowers(mode='test', transform=transform)
+
+            for i in range(2):
+                sample = flowers[i]
+                print(sample[0].shape, sample[1])
     """
 
     def __init__(self,
@@ -233,6 +322,20 @@ class CenterCropResize(object):
         size (int|list|tuple): Target size of output image, with (height, width) shape.
         crop_padding (int): center crop with the padding. Default: 32.
         interpolation (int): interpolation mode of resize. Default: cv2.INTER_LINEAR.
+
+    Examples:
+    
+        .. code-block:: python
+
+            from hapi.datasets import Flowers
+            from hapi.vision.transforms import Compose, Resize, CenterCropResize
+
+            transform = Compose([Resize(500), CenterCropResize(224)])
+            flowers = Flowers(mode='test', transform=transform)
+
+            for i in range(2):
+                sample = flowers[i]
+                print(sample[0].shape, sample[1])
     """
 
     def __init__(self, size, crop_padding=32, interpolation=cv2.INTER_LINEAR):
@@ -262,6 +365,20 @@ class CenterCrop(object):
 
     Args:
         output_size: Target size of output image, with (height, width) shape.
+    
+    Examples:
+    
+        .. code-block:: python
+
+            from hapi.datasets import Flowers
+            from hapi.vision.transforms import Compose, Resize, CenterCrop
+
+            transform = Compose([Resize(500), CenterCrop(224)])
+            flowers = Flowers(mode='test', transform=transform)
+
+            for i in range(2):
+                sample = flowers[i]
+                print(sample[0].shape, sample[1])
     """
 
     def __init__(self, output_size):
@@ -289,6 +406,20 @@ class RandomHorizontalFlip(object):
 
     Args:
         prob (float): probability of the input data being flipped. Default: 0.5
+
+    Examples:
+    
+        .. code-block:: python
+
+            from hapi.datasets import Flowers
+            from hapi.vision.transforms import Compose, RandomHorizontalFlip
+
+            transform = Compose([RandomHorizontalFlip()])
+            flowers = Flowers(mode='test', transform=transform)
+
+            for i in range(2):
+                sample = flowers[i]
+                print(sample[0].shape, sample[1])
     """
 
     def __init__(self, prob=0.5):
@@ -305,6 +436,20 @@ class RandomVerticalFlip(object):
 
     Args:
         prob (float): probability of the input data being flipped. Default: 0.5
+
+    Examples:
+    
+        .. code-block:: python
+
+            from hapi.datasets import Flowers
+            from hapi.vision.transforms import Compose, RandomVerticalFlip
+
+            transform = Compose([RandomVerticalFlip()])
+            flowers = Flowers(mode='test', transform=transform)
+
+            for i in range(2):
+                sample = flowers[i]
+                print(sample[0].shape, sample[1])
     """
 
     def __init__(self, prob=0.5):
@@ -325,6 +470,23 @@ class Normalize(object):
     Args:
         mean (int|float|list): Sequence of means for each channel.
         std (int|float|list): Sequence of standard deviations for each channel.
+
+    Examples:
+    
+        .. code-block:: python
+
+            from hapi.datasets import Flowers
+            from hapi.vision.transforms import Compose, Normalize, Permute
+
+            normalize = Normalize(mean=[123.675, 116.28, 103.53], 
+                                std=[58.395, 57.120, 57.375])
+
+            transform = Compose([Permute(), normalize])
+            flowers = Flowers(mode='test', transform=transform)
+
+            for i in range(2):
+                sample = flowers[i]
+                print(sample[0].shape, sample[1])
     
     """
 
@@ -351,6 +513,20 @@ class Permute(object):
     Args:
         mode: Output mode of input. Default: "CHW".
         to_rgb: convert 'bgr' image to 'rgb'. Default: True.
+
+    Examples:
+    
+        .. code-block:: python
+
+            from hapi.datasets import Flowers
+            from hapi.vision.transforms import Compose, Permute
+
+            transform = Compose([Permute()])
+            flowers = Flowers(mode='test', transform=transform)
+
+            for i in range(2):
+                sample = flowers[i]
+                print(sample[0].shape, sample[1])
     """
 
     def __init__(self, mode="CHW", to_rgb=True):
@@ -375,6 +551,20 @@ class GaussianNoise(object):
     Args:
         mean: Gaussian mean used to generate noise.
         std: Gaussian standard deviation used to generate noise.
+    
+    Examples:
+    
+        .. code-block:: python
+
+            from hapi.datasets import Flowers
+            from hapi.vision.transforms import Compose, GaussianNoise
+
+            transform = Compose([GaussianNoise()])
+            flowers = Flowers(mode='test', transform=transform)
+
+            for i in range(2):
+                sample = flowers[i]
+                print(sample[0].shape, sample[1])
     """
 
     def __init__(self, mean=0.0, std=1.0):
@@ -394,6 +584,20 @@ class BrightnessTransform(object):
     Args:
         value: How much to adjust the brightness. Can be any
             non negative number. 0 gives the original image
+
+    Examples:
+    
+        .. code-block:: python
+
+            from hapi.datasets import Flowers
+            from hapi.vision.transforms import Compose, BrightnessTransform
+
+            transform = Compose([BrightnessTransform(0.4)])
+            flowers = Flowers(mode='test', transform=transform)
+
+            for i in range(2):
+                sample = flowers[i]
+                print(sample[0].shape, sample[1])
     """
 
     def __init__(self, value):
@@ -418,6 +622,20 @@ class ContrastTransform(object):
     Args:
         value: How much to adjust the contrast. Can be any
             non negative number. 0 gives the original image
+
+    Examples:
+    
+        .. code-block:: python
+
+            from hapi.datasets import Flowers
+            from hapi.vision.transforms import Compose, ContrastTransform
+
+            transform = Compose([ContrastTransform(0.4)])
+            flowers = Flowers(mode='test', transform=transform)
+
+            for i in range(2):
+                sample = flowers[i]
+                print(sample[0].shape, sample[1])
     """
 
     def __init__(self, value):
@@ -443,6 +661,20 @@ class SaturationTransform(object):
     Args:
         value: How much to adjust the saturation. Can be any
             non negative number. 0 gives the original image
+
+    Examples:
+    
+        .. code-block:: python
+
+            from hapi.datasets import Flowers
+            from hapi.vision.transforms import Compose, SaturationTransform
+
+            transform = Compose([SaturationTransform(0.4)])
+            flowers = Flowers(mode='test', transform=transform)
+
+            for i in range(2):
+                sample = flowers[i]
+                print(sample[0].shape, sample[1])
     """
 
     def __init__(self, value):
@@ -469,6 +701,20 @@ class HueTransform(object):
     Args:
         value: How much to adjust the hue. Can be any number
             between 0 and 0.5, 0 gives the original image
+
+    Examples:
+    
+        .. code-block:: python
+
+            from hapi.datasets import Flowers
+            from hapi.vision.transforms import Compose, HueTransform
+
+            transform = Compose([HueTransform(0.4)])
+            flowers = Flowers(mode='test', transform=transform)
+
+            for i in range(2):
+                sample = flowers[i]
+                print(sample[0].shape, sample[1])
     """
 
     def __init__(self, value):
@@ -510,6 +756,20 @@ class ColorJitter(object):
         hue: How much to jitter hue.
             Chosen uniformly from [-hue, hue] or the given [min, max].
             Should have 0<= hue <= 0.5 or -0.5 <= min <= max <= 0.5.
+
+    Examples:
+    
+        .. code-block:: python
+
+            from hapi.datasets import Flowers
+            from hapi.vision.transforms import Compose, ColorJitter
+
+            transform = Compose([ColorJitter(0.4)])
+            flowers = Flowers(mode='test', transform=transform)
+
+            for i in range(2):
+                sample = flowers[i]
+                print(sample[0].shape, sample[1])
     """
 
     def __init__(self, brightness=0, contrast=0, saturation=0, hue=0):