def head_contained(anaphor, antecedent):
    """ Compute whether one mention's head is a substring of the other
    mention's head.

    Args:
        anaphor (Mention): A mention.
        antecedent (Mention): Another mention, preceding the anaphor.

    Returns:
        The tuple ('head_contained', CONTAINED), where CONTAINED is True if
        the anaphor's head contains the antecedent's head, or vice versa
        (ignoring case).
    """
    ana_head = anaphor.attributes["head_as_lowercase_string"]
    ante_head = antecedent.attributes["head_as_lowercase_string"]

    contained = ana_head in ante_head or ante_head in ana_head

    return "head_contained", contained