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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_most_available_stanza(self, peer_jid):
 """ Obtain the stanza describing the most-available presence of the contact. :param peer_jid: Bare JID of the contact. :type peer_jid: :class:`aioxmpp.JID` :rtype: :class:`aioxmpp.Presence` or :data:`None` :return: The presence stanza of the most available resource or :data:`None` if there is no available resource. The "most available" resource is the one whose presence state orderest highest according to :class:`~aioxmpp.PresenceState`. If there is no available resource for a given `peer_jid`, :data:`None` is returned. """

        presences = sorted(
            self.get_peer_resources(peer_jid).items(),
            key=lambda item: aioxmpp.structs.PresenceState.from_stanza(item[1])
        )
        if not presences:
            return None
        return presences[-1][1]