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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 subscribe(self, jid, node=None, *, subscription_jid=None, config=None):
 """ Subscribe to a node. :param jid: Address of the PubSub service. :type jid: :class:`aioxmpp.JID` :param node: Name of the PubSub node to subscribe to. :type node: :class:`str` :param subscription_jid: The address to subscribe to the service. :type subscription_jid: :class:`aioxmpp.JID` :param config: Optional configuration of the subscription :type config: :class:`~.forms.Data` :raises aioxmpp.errors.XMPPError: as returned by the service :return: The response from the server. :rtype: :class:`.xso.Request` By default, the subscription request will be for the bare JID of the client. It can be specified explicitly using the `subscription_jid` argument. If the service requires it or if it makes sense for other reasons, the subscription configuration :class:`~.forms.Data` form can be passed using the `config` argument. On success, the whole :class:`.xso.Request` object returned by the server is returned. It contains a :class:`.xso.Subscription` :attr:`~.xso.Request.payload` which has information on the nature of the subscription (it may be ``"pending"`` or ``"unconfigured"``) and the :attr:`~.xso.Subscription.subid` which may be required for other operations. On failure, the corresponding :class:`~.errors.XMPPError` is raised. """


        subscription_jid = subscription_jid or self.client.local_jid.bare()

        iq = aioxmpp.stanza.IQ(to=jid, type_=aioxmpp.structs.IQType.SET)
        iq.payload = pubsub_xso.Request(
            pubsub_xso.Subscribe(subscription_jid, node=node)
        )

        if config is not None:
            iq.payload.options = pubsub_xso.Options(
                subscription_jid,
                node=node
            )
            iq.payload.options.data = config

        response = yield from self.client.send(iq)
        return response