add return values sections

Author: rustagir

source/reference/method/MongoDBClientBulkWrite-createWithCollection.txt

@@ -73,6 +73,12 @@ Parameters
        - boolean
        - Specifies whether to return verbose results. The default is ``false``.
 
+Return Values
+-------------
+
+A new ``ClientBulkWrite`` object with an empty ``BulkWriteCommand``
+specification.
+
 Errors/Exceptions
 -----------------
 

source/reference/method/MongoDBClientBulkWrite-withCollection.txt

@@ -44,6 +44,12 @@ Parameters
   added to the ``ClientBulkWrite`` instance after calling
   ``withCollection()``.
 
+Return Values
+-------------
+
+A new ``ClientBulkWrite`` object with the same ``BulkWriteCommand``
+specification but an updated target namespace.
+
 Errors/Exceptions
 -----------------