code: def update(self, display_name=None, display_description=None):
          
          return self.manager.update(self, display_name=display_name,
                  display_description=display_description)
docs: Update the specified values on this snapshot. You may specify one or
          more values to update. If no values are specified as non-None, the call
          is a no-op; no exception will be raised.