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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_link(self, peer):
 """ Returns a link to the given peer :return: A Link object :raise ValueError: Unknown peer """

        assert isinstance(peer, beans.Peer)

        # Look for a link to the peer, using routers
        for router in self._routers:
            link = router.get_link(peer)
            if link:
                return link

        # Not found
        raise ValueError("No link to peer {0}".format(peer))