@classmethod
def _get_listen_keys(cls, attribute):
    """Given a descriptor attribute, return a ``set()`` of the attribute
        keys which indicate a change in the state of this attribute.

        This is normally just ``set([attribute.key])``, but can be overridden
        to provide for additional keys.  E.g. a :class:`.MutableComposite`
        augments this set with the attribute keys associated with the columns
        that comprise the composite value.

        This collection is consulted in the case of intercepting the
        :meth:`.InstanceEvents.refresh` and
        :meth:`.InstanceEvents.refresh_flush` events, which pass along a list
        of attribute names that have been refreshed; the list is compared
        against this set to determine if action needs to be taken.

        .. versionadded:: 1.0.5

        """
    return {attribute.key}
