document the save_entity will ignore properties whose value is empty list or none value

lucemia · lucemia · commit 15a507e946d0 · 2014-12-29T12:03:51.000+08:00
diff --git a/gcloud/datastore/connection.py b/gcloud/datastore/connection.py
@@ -380,6 +380,10 @@ def save_entity(self, dataset_id, key_pb, properties,
            will be replaced by those passed in 'properties';  properties
            not passed in 'properties' no longer be set for the entity.
 
+        .. note::
+           When saving an entity to the backend, properties whose value are
+           Empty lists or none cannot be saved and will be ignore.
+
         :type dataset_id: string
         :param dataset_id: The dataset in which to save the entity.
 
