def get_missing_face_hierarchical_keywords(iptc_data, face_list=None):
    """Checks if keywords need to be added for faces. Returns the keywords that need
       to be added."""
    missing_keywords = []
    if face_list == None:
        face_list = iptc_data.region_names
    for name in face_list:
        # Look for the full name or just the first name.
        if "People|" + name in iptc_data.hierarchical_subject:
            continue
        parts = name.split(" ")
        if len(parts) <= 1 or not "People|" + parts[0] in iptc_data.hierarchical_subject:
            missing_keywords.append("People|" + name)
    return missing_keywords