'Returns a string version of these replication options which are
suitable for use in a CREATE KEYSPACE statement.'

def export_for_schema(self):

    ret = "{'class':    'NetworkTopologyStrategy'"
    for (dc, repl_factor) in sorted(self.dc_replication_factors.items()):
        ret += (",    '%s':    '%d'" % (dc, repl_factor))
    return (ret + '}')
