Fix the docs bug in collective file. (#34374)

* fix the docs bug in collective file

python/paddle/distributed/collective.py

@@ -1341,6 +1341,7 @@ def split(x,
 
     Examples:
         .. code-block:: python
+
             # required: distributed
             import paddle
             import paddle.distributed.fleet as fleet
@@ -1456,6 +1457,7 @@ def split(x,
 def alltoall(in_tensor_list, out_tensor_list, group=None, use_calc_stream=True):
     """
     Scatter tensors in in_tensor_list to all participators and gather the result tensors in out_tensor_list.
+    
     Args:
         in_tensor_list (list): A list of input Tensors. Every element in the list must be a Tensor whose data type
             should be float16, float32, float64, int32 or int64.
@@ -1463,14 +1465,18 @@ def alltoall(in_tensor_list, out_tensor_list, group=None, use_calc_stream=True):
             data type of the input Tensors.
         group (Group, optional): The group instance return by new_group or None for global default group. Default: None.
         use_calc_stream (bool, optional): Wether to use calculation stream (True) or communication stream. Default: True.
+    
     Returns:
         None.
+    
     Examples:
         .. code-block:: python
+
             # required: distributed
             import numpy as np
             import paddle
             from paddle.distributed import init_parallel_env
+            
             init_parallel_env()
             out_tensor_list = []
             if paddle.distributed.ParallelEnv().rank == 0:
@@ -1535,14 +1541,17 @@ def send(tensor, dst=0, group=None, use_calc_stream=True):
         dst (int): The destination rank id.
         group (Group, optional): The group instance return by new_group or None for global default group. Default: None.
         use_calc_stream (bool, optional): Whether to use calculate stream or communication stream. Default: True.
+    
     Returns:
         None.
 
     Examples:
         .. code-block:: python
+
             # required: distributed
             import paddle
             from paddle.distributed import init_parallel_env
+
             init_parallel_env()
             if paddle.distributed.ParallelEnv().rank == 0:
                 data = paddle.to_tensor([7, 8, 9])
@@ -1585,14 +1594,17 @@ def recv(tensor, src=0, group=None, use_calc_stream=True):
         src (int): The source rank id.
         group (Group, optional): The group instance return by new_group or None for global default group. Default: None.
         use_calc_stream (bool, optional): Whether to use calculate stream or communication stream. Default: True.
+    
     Returns:
         None.
 
     Examples:
         .. code-block:: python
+
             # required: distributed
             import paddle
             from paddle.distributed import init_parallel_env
+
             init_parallel_env()
             if paddle.distributed.ParallelEnv().rank == 0:
                 data = paddle.to_tensor([7, 8, 9])