[xdoctest][task 248-249,266-267,269] reformat example code with google style...

[xdoctest][task 248-249,266-267,269] reformat example code with google style in `incubate/distributed/fleet/*`,`incubate/nn/layer/*` (#56772)

* [Doctest]fix No.248-249,266-267,269, test=docs_preview

* fix style

* fix

* add env:DISTRIBUTED

python/paddle/incubate/distributed/fleet/parameter_server/ir/ps_dispatcher.py

@@ -55,11 +55,13 @@ class HashName(PSDispatcher):
     Examples:
         .. code-block:: python
 
-        pserver_endpoints = ["127.0.0.1:6007", "127.0.0.1:6008"]
-        vars = ["var1","var2","var3","var4","var5"]
+            >>> from paddle.incubate.distributed.fleet.parameter_server.ir.ps_dispatcher import RoundRobin
 
-        rr = RoundRobin(pserver_endpoints)
-        rr.dispatch(vars)
+            >>> pserver_endpoints = ["127.0.0.1:6007", "127.0.0.1:6008"]
+            >>> vars = ["var1","var2","var3","var4","var5"]
+
+            >>> rr = HashName(pserver_endpoints)
+            >>> rr.dispatch(vars)
 
     """
 
@@ -95,11 +97,13 @@ class RoundRobin(PSDispatcher):
     Examples:
         .. code-block:: python
 
-        pserver_endpoints = ["127.0.0.1:6007", "127.0.0.1:6008"]
-        vars = ["var1","var2","var3","var4","var5"]
+            >>> from paddle.incubate.distributed.fleet.parameter_server.ir.ps_dispatcher import RoundRobin
+
+            >>> pserver_endpoints = ["127.0.0.1:6007", "127.0.0.1:6008"]
+            >>> vars = ["var1","var2","var3","var4","var5"]
 
-        rr = RoundRobin(pserver_endpoints)
-        rr.dispatch(vars)
+            >>> rr = RoundRobin(pserver_endpoints)
+            >>> rr.dispatch(vars)
 
     """
 

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

@@ -46,15 +46,17 @@ class FusedEcMoe(Layer):
     Examples:
         .. code-block:: python
 
-            # required: gpu
-            import paddle
-            from paddle.incubate.nn.layer.fused_ec_moe import FusedEcMoe
+            >>> # doctest: +REQUIRES(env:GPU)
+            >>> import paddle
+            >>> paddle.device.set_device('gpu')
+            >>> from paddle.incubate.nn.layer.fused_ec_moe import FusedEcMoe
 
-            x = paddle.randn([10, 128, 1024]) # [bsz, seq_len, d_model]
-            gate = paddle.randn([10, 128, 8]) # [bsz, seq_len, num_experts]
-            moe = FusedEcMoe(1024, 4096, 8, act_type="gelu")
-            y = moe(x, gate)
-            print(y.shape) # [10, 128, 1024]
+            >>> x = paddle.randn([10, 128, 1024]) # [bsz, seq_len, d_model]
+            >>> gate = paddle.randn([10, 128, 8]) # [bsz, seq_len, num_experts]
+            >>> moe = FusedEcMoe(1024, 4096, 8, act_type="gelu")
+            >>> y = moe(x, gate)
+            >>> print(y.shape)
+            [10, 128, 1024]
     """
 
     def __init__(

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

@@ -56,14 +56,16 @@ class FusedLinear(Layer):
     Examples:
         .. code-block:: python
 
-            # required: gpu
-            import paddle
-            from paddle.incubate.nn import FusedLinear
+            >>> # doctest: +REQUIRES(env:GPU)
+            >>> import paddle
+            >>> paddle.device.set_device('gpu')
+            >>> from paddle.incubate.nn import FusedLinear
 
-            x = paddle.randn([3, 4])
-            linear = FusedLinear(4, 5)
-            y = linear(x)
-            print(y.shape) # [3, 5]
+            >>> x = paddle.randn([3, 4])
+            >>> linear = FusedLinear(4, 5)
+            >>> y = linear(x)
+            >>> print(y.shape)
+            [3, 5]
     """
 
     def __init__(

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

@@ -55,21 +55,25 @@ class ListenAndServ:
     Examples:
         .. code-block:: python
 
-            import paddle.fluid as fluid
-            import paddle
-            with fluid.program_guard(main):
-                serv = layers.ListenAndServ(
-                    "127.0.0.1:6170", ["X"], optimizer_mode=False)
-                with serv.do():
-                    x = paddle.static.data(
-                        shape=[32, 32],
-                        dtype='float32',
-                        name="X")
-                    paddle.nn.initializer.Constant(value=1.0)(x, main.global_block())
-                    paddle.scale(x=x, scale=10.0, out=out_var)
-
-            exe = fluid.Executor(place)
-            exe.run(main)
+            >>> # doctest: +REQUIRES(env:DISTRIBUTED)
+            >>> from paddle.incubate.nn.layer.io import ListenAndServ
+            >>> import paddle
+            >>> paddle.enable_static()
+            >>> place = paddle.CPUPlace()
+            >>> main = paddle.static.Program()
+            >>> with paddle.static.program_guard(main):
+            ...     serv = ListenAndServ(
+            ...         "127.0.0.1:6170", ["X"], optimizer_mode=False)
+            ...     with serv.do():
+            ...         x = paddle.static.data(
+            ...             shape=[32, 32],
+            ...             dtype='float32',
+            ...             name="X")
+            ...         paddle.nn.initializer.Constant(value=1.0)(x, main.global_block())
+            ...         paddle.scale(x=x, scale=10.0)
+
+            >>> exe = paddle.static.Executor(place)
+            >>> exe.run(main)
     """
 
     def __init__(self, endpoint, inputs, fan_in=1, optimizer_mode=True):
@@ -115,7 +119,9 @@ class ListenAndServ:
         return parent_block
 
     def complete_op(self):
-        from paddle.incubate.fleet.parameter_server.mode import DistributedMode
+        from paddle.incubate.distributed.fleet.parameter_server.mode import (
+            DistributedMode,
+        )
 
         main_program = self.helper.main_program
         current_block = main_program.current_block()