def METHOD_NAME(keyspace=None):
    """
    Return existing column families for all keyspaces
    or just the provided one.
    CLI Example:
    .. code-block:: bash
        salt '*' cassandra.column_families
        salt '*' cassandra.column_families <keyspace>
    """
    sys = _sys_mgr()
    ksps = sys.list_keyspaces()
    if keyspace:
        if keyspace in ksps:
            return list(sys.get_keyspace_column_families(keyspace).keys())
        else:
            return None
    else:
        ret = {}
        for kspace in ksps:
            ret[kspace] = list(sys.get_keyspace_column_families(kspace).keys())
        return ret