Add utility method to convert lists to csv.

Author: Mike Kistler

watson_developer_cloud/watson_service.py

@@ -227,6 +227,12 @@ def _convert_model(val):
             return val._to_dict()
         return val
 
+    @staticmethod
+    def _convert_list(val):
+        if isinstance(val, list):
+            return ",".join(val)
+        return val
+
     @staticmethod
     def _encode_path_vars(*args):
         return (requests.utils.quote(x, safe='') for x in args)