[xdoctest] reformat example code with google style in No. 264-265 (#56907)

* Fix styles of code

* update the GPU option

* add the GPU setup

* remove the note

* update the code

python/paddle/incubate/nn/layer/fused_dropout_add.py

@@ -44,16 +44,17 @@ class FusedDropoutAdd(Layer):
     Examples:
         .. code-block:: python
 
-            # required: gpu
-            import paddle
-            from paddle.incubate.nn.layer.fused_dropout_add import FusedDropoutAdd
+            >>> # doctest: +REQUIRES(env:GPU)
+            >>> import paddle
+            >>> paddle.device.set_device('gpu')
+            >>> from paddle.incubate.nn.layer.fused_dropout_add import FusedDropoutAdd
 
-            x = paddle.to_tensor([[1,2,3], [4,5,6]], dtype="float32")
-            y = paddle.to_tensor([[1,2,3], [4,5,6]], dtype="float32")
+            >>> x = paddle.to_tensor([[1,2,3], [4,5,6]], dtype="float32")
+            >>> y = paddle.to_tensor([[1,2,3], [4,5,6]], dtype="float32")
 
-            m = FusedDropoutAdd(p=0.5)
+            >>> m = FusedDropoutAdd(p=0.5)
 
-            out = m(x, y)
+            >>> out = m(x, y)
     """
 
     def __init__(self, p=0.5, mode="upscale_in_train", name=None):

python/paddle/incubate/nn/layer/fused_dropout_nd.py

@@ -53,23 +53,23 @@ class FusedDropout(paddle.nn.Layer):
     Examples:
         .. code-block:: python
 
-            import paddle
-
-            x = paddle.to_tensor([[1, 2, 3], [4, 5, 6]], dtype="float32")
-            m = paddle.incubate.nn.FusedDropout(p=0.5)
-
-            y_train = m(x)
-            print(y_train)
-            # Tensor(shape=[2, 3], dtype=float32, place=Place(gpu:0), stop_gradient=True,
-            #        [[2., 0., 6.],
-            #         [0., 0., 0.]])
-
-            m.eval()  # switch the model to test phase
-            y_test = m(x)
-            print(y_test)
-            # Tensor(shape=[2, 3], dtype=float32, place=Place(gpu:0), stop_gradient=True,
-            #        [[1., 2., 3.],
-            #         [4., 5., 6.]])
+            >>> import paddle
+
+            >>> x = paddle.to_tensor([[1, 2, 3], [4, 5, 6]], dtype="float32")
+            >>> m = paddle.incubate.nn.FusedDropout(p=0.5)
+
+            >>> y_train = m(x)
+            >>> print(y_train)
+            Tensor(shape=[2, 3], dtype=float32, place=Place(cpu), stop_gradient=True,
+                   [[2., 0., 6.],
+                    [0., 0., 0.]])
+
+            >>> m.eval()  # switch the model to test phase
+            >>> y_test = m(x)
+            >>> print(y_test)
+            Tensor(shape=[2, 3], dtype=float32, place=Place(cpu), stop_gradient=True,
+                   [[1., 2., 3.],
+                    [4., 5., 6.]])
     """
 
     def __init__(self, p=0.5, axis=None, mode="upscale_in_train", name=None):