fix Layer.__dir__ to show the parameters/sublayers/buffers/attr/method of the Layer (#25197)

* show the attr and functions of the Layer,test=develop

* add buffer for dir,test=develop

* fix __dir__,test=develop

* fix doc of Layer.__dir__, test=develop

python/paddle/fluid/dygraph/layers.py

@@ -752,6 +752,41 @@ class Layer(core.Layer):
         else:
             object.__delattr__(self, name)
 
+    def __dir__(self):
+        """
+        Return a list. Get all parameters, buffers(non-parameter variables), sublayers, method and attr of Layer.
+
+        Examples:
+            import paddle.fluid as fluid
+            import numpy as np
+
+            fluid.dygraph.enable_dygraph()
+
+            class Mylayer(fluid.dygraph.Layer):
+                def __init__(self):
+                    super(Mylayer, self).__init__()
+                    self.linear1 = fluid.dygraph.Linear(10, 10)
+                    self.linear2 = fluid.dygraph.Linear(5, 5)
+                    self.conv2d = fluid.dygraph.Conv2D(3, 2, 3)
+                    self.embedding = fluid.dygraph.Embedding(size=[128, 16])
+                    self.h_0 = fluid.dygraph.to_variable(np.zeros([10, 10]).astype('float32'))
+
+            mylayer = Mylayer()
+            print(dir(mylayer))
+            # only parts are shown, because of list have too much content
+            # ['__call__', '__class__',  ... , 'conv2d', 'embedding', 'h_0', 'linear1', 'linear2', ... , 'sublayers', 'train']
+
+        """
+        method = dir(self.__class__)
+        attrs = list(self.__dict__.keys())
+        parameters = list(self._parameters.keys())
+        sublayers = list(self._sub_layers.keys())
+        buffers = list(self._buffers.keys())
+
+        keys = method + attrs + parameters + sublayers + buffers
+
+        return keys
+
     def state_dict(self,
                    destination=None,
                    include_sublayers=True,

python/paddle/fluid/tests/unittests/test_imperative_named_members.py

@@ -79,6 +79,41 @@ class TestImperativeNamedParameters(unittest.TestCase):
 
             self.assertListEqual(expected_named_parameters, named_parameters)
 
+    def test_dir_layer(self):
+        with fluid.dygraph.guard():
+
+            class Mymodel(fluid.dygraph.Layer):
+                def __init__(self):
+                    super(Mymodel, self).__init__()
+                    self.linear1 = fluid.dygraph.Linear(10, 10)
+                    self.linear2 = fluid.dygraph.Linear(5, 5)
+                    self.conv2d = fluid.dygraph.Conv2D(3, 2, 3)
+                    self.embedding = fluid.dygraph.Embedding(size=[128, 16])
+                    self.h_0 = fluid.dygraph.to_variable(
+                        np.zeros([10, 10]).astype('float32'))
+                    self.weight = self.create_parameter(
+                        shape=[2, 3],
+                        attr=fluid.ParamAttr(),
+                        dtype="float32",
+                        is_bias=False)
+
+            model = Mymodel()
+
+            expected_members = dir(model)
+
+            self.assertTrue("linear1" in expected_members,
+                            "model should contain Layer: linear1")
+            self.assertTrue("linear2" in expected_members,
+                            "model should contain Layer: linear2")
+            self.assertTrue("conv2d" in expected_members,
+                            "model should contain Layer: conv2d")
+            self.assertTrue("embedding" in expected_members,
+                            "model should contain Layer: embedding")
+            self.assertTrue("h_0" in expected_members,
+                            "model should contain buffer: h_0")
+            self.assertTrue("weight" in expected_members,
+                            "model should contain parameter: weight")
+
 
 if __name__ == '__main__':
     unittest.main()