def getRelationTokens(query=None):
    """return tokens for given intransitive query, or all relation tokens.

        Returns a None if no Tokens for query.

        This also happens to be equivalent to `findRelationTokens` with
        a maxDepth of 1, and no other arguments other than the optional
        query, except that if there are no matches, `findRelationTokens`
        returns an empty set (so it *always* returns an iterable). """
