def _delete_value(self, entity):
if self._name in entity._values:<EOL><INDENT>del entity._values[self._name]<EOL><DEDENT>
Internal helper to delete the value for this Property from an entity.

        Note that if no value exists this is a no-op; deleted values will
        not be serialized but requesting their value will return None (or
        an empty list in the case of a repeated Property).