add example for maxpool

mindspore/ops/operations/nn_ops.py

@@ -915,7 +915,7 @@ class MaxPool(_Pool):
         Tensor, with shape :math:`(N, C_{out}, H_{out}, W_{out})`.
 
     Examples:
-        >>> input_tensor = Tensor(np.arange(1*3*3*4).reshape((1,3,3,4)),mindspore.float32)
+        >>> input_tensor = Tensor(np.arange(1 * 3 * 3 * 4).reshape((1, 3, 3, 4)), mindspore.float32)
         >>> maxpool_op = P.MaxPool(padding="VALID", ksize=2, strides=1)
         >>> output_tensor = maxpool_op(input_tensor)
     """
@@ -966,7 +966,7 @@ class MaxPoolWithArgmax(_Pool):
         - **mask** (Tensor) -  Max values' index represented by the mask.
 
     Examples:
-        >>> input_tensor = Tensor(np.arange(1*3*3*4).reshape((1,3,3,4)),mindspore.float32)
+        >>> input_tensor = Tensor(np.arange(1 * 3 * 3 * 4).reshape((1, 3, 3, 4)), mindspore.float32)
         >>> maxpool_arg_op = P.MaxPoolWithArgmax(padding="VALID", ksize=2, strides=1)
         >>> output_tensor, argmax = maxpool_arg_op(input_tensor)
     """