Fix some sample codes in api2.0，include zeros, pow, mul, ones_like, zeros_like

In those ops, some api has execute run error, fix those op, and format some sample code.

python/paddle/tensor/creation.py

@@ -207,7 +207,7 @@ def ones(shape, dtype=None, out=None, device=None):
 
           import paddle
           data = paddle.ones(shape=[3, 2], dtype='float32') # [[1., 1.], [1., 1.], [1., 1.]]
-          data = paddle.ones(shape=[2, 2], dtype='float32', device='cpu') # [[1., 1.], [1., 0.]]
+          data = paddle.ones(shape=[2, 2], dtype='float32', device='cpu') # [[1., 1.], [1., 1.]]
     """
     check_dtype(dtype, 'create data type',
                 ['bool', 'float16', 'float32', 'float64', 'int32', 'int64'],
@@ -247,7 +247,7 @@ def ones_like(input, dtype=None, device=None, name=None):
           import paddle
           import paddle.fluid as fluid
 
-          x = fluid.layers.data(name='x', dtype='float32', shape=[3], append_batch_size=False)
+          x = fluid.data(name='x', dtype='float32', shape=[3])
           data = paddle.ones_like(x) # data=[1.0, 1.0, 1.0]
           data1 = paddle.ones_like(input=x, device="gpu") data1=[1.0, 1.0. 1.0]
 
@@ -354,9 +354,9 @@ def zeros_like(input, dtype=None, device=None, name=None):
           import paddle
           import paddle.fluid as fluid
 
-          x = fluid.layers.data(name='x', dtype='float32', shape=[3], append_batch_size=False)
+          x = fluid.data(name='x', dtype='float32', shape=[3])
           data = paddle.ones_like(x) # data=[1.0, 1.0, 1.0]
-          data1 = paddle.ones_like(input=x, device="gpu") data1=[1.0, 1.0. 1.0]
+          data1 = paddle.ones_like(input=x, device="gpu") #data1=[1.0, 1.0. 1.0]
 
     """
 

python/paddle/tensor/linalg.py

@@ -96,6 +96,7 @@ def matmul(x, y, transpose_x=False, transpose_y=False, alpha=1.0, name=None):
             # x: [M], y: [N]
             # paddle.matmul(x, y, True, True)  # out: [M, N]
 
+            import paddle
             import paddle.fluid as fluid
             x = fluid.data(name='x', shape=[2, 3], dtype='float32')
             y = fluid.data(name='y', shape=[3, 2], dtype='float32')

python/paddle/tensor/math.py

@@ -168,18 +168,19 @@ def pow(input, exponent, out=None, name=None):
         .. code-block:: python
 
             import paddle
+            import paddle.fluid as fluid
 
-            x = paddle.fluid.data(name="x", shape=[32,32], dtype="float32")
+            x = fluid.data(name="x", shape=[32,32], dtype="float32")
 
             # example 1: argument exponent is float
-            res = paddle.fluid.data(name="output", shape=[32,32], dtype="float32")
+            res = fluid.data(name="output", shape=[32,32], dtype="float32")
             y_1 = paddle.pow(x, 2.0, out=res)
             # y_1 is x^{2.0}
 
             # example 2: argument exponent is Variable
             exponet_tensor = fluid.layers.fill_constant([1], "float32", 3.0)
-            res = paddle.fluid.data(name="output", shape=[32,32], dtype="float32")
-            y_2 = paddle.pow(x, exponent_tensor, out=res)
+            res = fluid.data(name="output", shape=[32,32], dtype="float32")
+            y_2 = paddle.pow(x, exponet_tensor, out=res)
             # y_2 is x^{3.0}
     """
     helper = LayerHelper('pow', **locals())
@@ -254,10 +255,11 @@ def mul(x, y, x_num_col_dims=1, y_num_col_dims=1, out=None, name=None):
         ..  code-block:: python
             
             import paddle
-            dataX = paddle.fluid.data(name="dataX", append_batch_size = False, shape=[2, 5], dtype="float32")
-            dataY = paddle.fluid.data(name="dataY", append_batch_size = False, shape=[5, 3], dtype="float32")
+            import paddle.fluid as fluid
+            dataX = fluid.data(name="dataX", shape=[2, 5], dtype="float32")
+            dataY = fluid.data(name="dataY", shape=[5, 3], dtype="float32")
             
-            res = paddle.fluid.data(name="output", append_batch_size = False, shape=[2, 3], dtype="float32")
+            res = fluid.data(name="output", shape=[2, 3], dtype="float32")
             output = paddle.mul(dataX, dataY,
                                       x_num_col_dims = 1,
                                       y_num_col_dims = 1,