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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 close(self):
 """ Unclaim the PEP node and unregister the registered features. It is not necessary to call close if this claim is managed by :class:`~aioxmpp.pep.register_pep_node`. """

        if self._closed:
            return

        self._closed = True
        self._pep_service._unclaim(self.node_namespace)
        self._unregister()