'Gets trunk object for port_id. None if not trunk.'

def get_trunk(self, context, port_id):

    if (port_id not in self._trunk_by_port_id):
        LOG.debug('Cache    miss    for    port    %s,    fetching    from    server', port_id)
        self.put_trunk(port_id, self._fetch_trunk(context, port_id))
        return self.get_trunk(context, port_id)
    return self._trunk_by_port_id[port_id]
