def isSubscribed(entity):
    """
        Returns whether entity has any subscription to this node.

        Only returns C{True} when the subscription state (if present) is
        C{'subscribed'} for any subscription that matches the bare JID.

        @param subscriber: bare JID of the subscriptions' entity.
        @type subscriber: L{JID<twisted.words.protocols.jabber.jid.JID>}
        @return: deferred that returns a C{bool}.
        """
