!9628 optimize example

From: @caozhou_huawei
Reviewed-by: @zh_qh,@kingxian
Signed-off-by: @kingxian

mindspore/train/serialization.py

@@ -345,7 +345,9 @@ def load_param_into_net(net, parameter_dict, strict_load=False):
         >>> net = Net()
         >>> ckpt_file_name = "./checkpoint/LeNet5-1_32.ckpt"
         >>> param_dict = load_checkpoint(ckpt_file_name, filter_prefix="conv1")
-        >>> load_param_into_net(net, param_dict)
+        >>> param_not_load = load_param_into_net(net, param_dict)
+        >>> print(param_not_load)
+        ['conv1.weight']
     """
     if not isinstance(net, nn.Cell):
         logger.error("Failed to combine the net and the parameters.")