Modify the docs for Transformer's APIs. test=document_fix (#27729)

python/paddle/nn/layer/transformer.py

@@ -644,7 +644,7 @@ class TransformerDecoderLayer(Layer):
             `weight_attr` to create parameters. Default: None, which means the
             default weight parameter property is used. See usage for details
             in :ref:`api_fluid_ParamAttr` . 
-        bias_attr (ParamAttr|tuple, optional): To specify the bias parameter property.
+        bias_attr (ParamAttr|tuple|bool, optional): To specify the bias parameter property.
             If it is a tuple, `bias_attr[0]` would be used as `bias_attr` for
             self attention, `bias_attr[1]` would be used as `bias_attr` for
             cross attention, and `bias_attr[2]` would be used as `bias_attr`
@@ -982,12 +982,12 @@ class Transformer(Layer):
     applies another layer normalization on the output of last encoder/decoder layer.
 
     Parameters:
-        d_model (int): The expected feature size in the encoder/decoder input
-            and output.
-        nhead (int): The number of heads in multi-head attention(MHA).
-        num_encoder_layers (int): The number of layers in encoder.
-        num_encoder_layers (int): The number of layers in decoder.
-        dim_feedforward (int): The hidden layer size in the feedforward network(FFN).
+        d_model (int, optional): The expected feature size in the encoder/decoder input
+            and output. Default 512
+        nhead (int, optional): The number of heads in multi-head attention(MHA). Default 8
+        num_encoder_layers (int, optional): The number of layers in encoder. Default 6
+        num_decoder_layers (int, optional): The number of layers in decoder. Default 6
+        dim_feedforward (int, optional): The hidden layer size in the feedforward network(FFN). Default 2048
         dropout (float, optional): The dropout probability used in pre-process
             and post-precess of MHA and FFN sub-layer. Default 0.1
         activation (str, optional): The activation function in the feedforward
@@ -1015,7 +1015,7 @@ class Transformer(Layer):
             Default: None, which means the default weight parameter property is used. 
             See usage for details
             in :code:`ParamAttr` . 
-        bias_attr (ParamAttr|tuple, optional): To specify the bias parameter property.
+        bias_attr (ParamAttr|tuple|bool, optional): To specify the bias parameter property.
             If it is a tuple, the length of `bias_attr` could be 1, 2 or 3. If it is 3, 
             `bias_attr[0]` would be used as `bias_attr` for self attention, `bias_attr[1]` 
             would be used as `bias_attr` for cross attention of `TransformerDecoder`, 
@@ -1028,9 +1028,9 @@ class Transformer(Layer):
             The `False` value means the corresponding layer would not have trainable 
             bias parameter. See usage for details in :code:`ParamAttr` . 
             Default: None,which means the default bias parameter property is used.
-        custom_encoder (Layer): If custom encoder is provided, use it as the encoder.
+        custom_encoder (Layer, optional): If custom encoder is provided, use it as the encoder.
             Default None
-        custom_decoder (Layer): If custom decoder is provided, use it as the decoder.
+        custom_decoder (Layer, optional): If custom decoder is provided, use it as the decoder.
             Default None
 
     Examples: