code: def __update_action(self, revision):
          
  
          patch = revision.get("patch")
          if patch.get("_id"):
              del patch["_id"]
  
          update_response = yield self.collection.patch(revision.get("master_id"), self.__make_storeable_patch_patchable(patch))
  
          if update_response.get("n") == 0:
              raise RevisionNotFoundException()
docs: Update a master document and revision history document
  
          :param dict revision: The revision dictionary