fix format

python/paddle/fluid/layers/io.py

@@ -109,7 +109,7 @@ class BlockGuardServ(BlockGuard):
 
 class ListenAndServ(object):
     """
-    ***ListenAndServ Layer***
+    **ListenAndServ Layer**
     
     ListenAndServ is used to create a rpc server bind and listen
     on specific TCP port, this server will run the sub-block when
@@ -121,9 +121,6 @@ class ListenAndServ(object):
         fan_in(int): how many client are expected to report to this server, default: 1.
         optimizer_mode(bool): whether to run the server as a parameter server, default: True.
 
-    Returns:
-        None
-
     Examples:
         .. code-block:: python
 

python/paddle/fluid/layers/nn.py

@@ -1049,7 +1049,7 @@ def chunk_eval(input,
                num_chunk_types,
                excluded_chunk_types=None):
     """
-    ***Chunk Evaluator***
+    **Chunk Evaluator**
 
     This function computes and outputs the precision, recall and
     F1-score of chunk detection.
@@ -1883,7 +1883,7 @@ def conv2d_transpose(input,
                      act=None,
                      name=None):
     """
-    ***Convlution2D Transpose Layer****
+    **Convlution2D Transpose Layer**
 
     The convolution2D transpose layer calculates the output based on the input,
     filter, and dilations, strides, paddings. Input(Input) and output(Output)