modify doc for ParameterList and LayerList (#27609)

* modify doc for ParameterList and LayerList, test=develop

* add empty line after code-block, test=develop

python/paddle/fluid/dygraph/container.py

@@ -98,15 +98,15 @@ class ParameterList(Layer):
     Examples:
         .. code-block:: python
 
-            import paddle.fluid as fluid
+            import paddle
             import numpy as np
 
-            class MyLayer(fluid.Layer):
+            class MyLayer(paddle.nn.Layer):
                 def __init__(self, num_stacked_param):
                     super(MyLayer, self).__init__()
                     # create ParameterList with iterable Parameters
-                    self.params = fluid.dygraph.ParameterList(
-                        [fluid.layers.create_parameter(
+                    self.params = paddle.nn.ParameterList(
+                        [paddle.create_parameter(
                             shape=[2, 2], dtype='float32')] * num_stacked_param)
 
                 def forward(self, x):
@@ -123,19 +123,18 @@ class ParameterList(Layer):
                     return x
 
             data_np = np.random.uniform(-1, 1, [5, 2]).astype('float32')
-            with fluid.dygraph.guard():
-                x = fluid.dygraph.to_variable(data_np)
+            x = paddle.to_tensor(data_np)
             num_stacked_param = 4
             model = MyLayer(num_stacked_param)
             print(len(model.params))  # 4
             res = model(x)
             print(res.shape)  # [5, 2]
 
-                replaced_param = fluid.layers.create_parameter(shape=[2, 3], dtype='float32')
+            replaced_param = paddle.create_parameter(shape=[2, 3], dtype='float32')
             model.params[num_stacked_param - 1] = replaced_param  # replace last param
             res = model(x)
             print(res.shape)  # [5, 3]
-                model.params.append(fluid.layers.create_parameter(shape=[3, 4], dtype='float32'))  # append param
+            model.params.append(paddle.create_parameter(shape=[3, 4], dtype='float32'))  # append param
             print(len(model.params))  # 5
             res = model(x)
             print(res.shape)  # [5, 4]
@@ -182,14 +181,15 @@ class LayerList(Layer):
 
     Examples:
         .. code-block:: python
-            import paddle.fluid as fluid
+
+            import paddle
             import numpy as np
 
-            class MyLayer(fluid.Layer):
+            class MyLayer(paddle.nn.Layer):
                 def __init__(self):
                     super(MyLayer, self).__init__()
-                    self.linears = fluid.dygraph.LayerList(
-                        [fluid.dygraph.Linear(10, 10) for i in range(10)])
+                    self.linears = paddle.nn.LayerList(
+                        [paddle.nn.Linear(10, 10) for i in range(10)])
 
                 def forward(self, x):
                     # LayerList can act as an iterable, or be indexed using ints
@@ -238,11 +238,11 @@ class LayerList(Layer):
 
         Examples:
             .. code-block:: python
-                import paddle.fluid as fluid
 
-                with fluid.dygraph.guard():
-                    linears = fluid.dygraph.LayerList([fluid.dygraph.Linear(10, 10) for i in range(10)])
-                    another = fluid.dygraph.Linear(10, 10)
+                import paddle
+
+                linears = paddle.nn.LayerList([paddle.nn.Linear(10, 10) for i in range(10)])
+                another = paddle.nn.Linear(10, 10)
                 linears.append(another)
                 print(len(linears))  # 11
         """
@@ -259,11 +259,11 @@ class LayerList(Layer):
 
         Examples:
             .. code-block:: python
-                import paddle.fluid as fluid
 
-                with fluid.dygraph.guard():
-                    linears = fluid.dygraph.LayerList([fluid.dygraph.Linear(10, 10) for i in range(10)])
-                    another = fluid.dygraph.Linear(10, 10)
+                import paddle
+
+                linears = paddle.nn.LayerList([paddle.nn.Linear(10, 10) for i in range(10)])
+                another = paddle.nn.Linear(10, 10)
                 linears.insert(3, another)
                 print(linears[3] is another)  # True
         """
@@ -283,11 +283,11 @@ class LayerList(Layer):
 
         Examples:
             .. code-block:: python
-                import paddle.fluid as fluid
 
-                with fluid.dygraph.guard():
-                    linears = fluid.dygraph.LayerList([fluid.dygraph.Linear(10, 10) for i in range(10)])
-                    another_list = fluid.dygraph.LayerList([fluid.dygraph.Linear(10, 10) for i in range(5)])
+                import paddle
+
+                linears = paddle.nn.LayerList([paddle.nn.Linear(10, 10) for i in range(10)])
+                another_list = paddle.nn.LayerList([paddle.nn.Linear(10, 10) for i in range(5)])
                 linears.extend(another_list)
                 print(len(linears))  # 15
                 print(another_list[0] is linears[10])  # True