Update example codes of ConstantInitializer & MSRAInitializer (#27915)

* Add api of constant in paddle.nn.initializer

* Add api of constant in paddle.nn.initializer

* Add api of constant in paddle.nn.initializer

* Add api of constant in paddle.nn.initializer

* Add api of constant in paddle.nn.initializer

* Add api of constant in paddle.nn.initializer

* Add api of constant in paddle.nn.initializer

* Add api of KaimingUniform & KaimingNormal in paddle.nn.initializer

* Add api of KaimingUniform & KaimingNormal in paddle.nn.initializer

* Add api of KaimingUniform & KaimingNormal in paddle.nn.initializer

* Add api of KaimingUniform & KaimingNormal in paddle.nn.initializer

* Add api of KaimingUniform & KaimingNormal in paddle.nn.initializer

* Add api of KaimingUniform & KaimingNormal in paddle.nn.initializer

* test=document_fix

* test=document_fix

python/paddle/fluid/initializer.py

@@ -105,10 +105,14 @@ class ConstantInitializer(Initializer):
     Examples:
         .. code-block:: python
 
-    	    import paddle.fluid as fluid
+            import paddle
+            import paddle.fluid as fluid
+            paddle.enable_static()
             x = fluid.data(name="data", shape=[8, 32, 32], dtype="float32")
-	    fc = fluid.layers.fc(input=x, size=10,
-    		param_attr=fluid.initializer.Constant(value=2.0))
+            fc = fluid.layers.fc(
+                input=x,
+                size=10,
+                param_attr=fluid.initializer.Constant(value=2.0))
 
     """
 
@@ -623,7 +627,9 @@ class MSRAInitializer(Initializer):
     Examples:
         .. code-block:: python
 
+            import paddle
             import paddle.fluid as fluid
+            paddle.enable_static()
             x = fluid.data(name="data", shape=[8, 32, 32], dtype="float32")
             fc = fluid.layers.fc(input=x, size=10,
                 param_attr=fluid.initializer.MSRA(uniform=False))