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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 query_topology_db(self, dict_convert=False, **req):
 """Query an entry to the topology DB. """

        session = db.get_session()
        with session.begin(subtransactions=True):
            try:
                # Check if entry exists.
                topo_disc = session.query(DfaTopologyDb).filter_by(**req).all()
            except orm_exc.NoResultFound:
                LOG.info("No Topology results found for %s", req)
                return None
        if dict_convert:
            return self._convert_topo_obj_dict(topo_disc)
        return topo_disc