gistfile1.py

for Model, relations in RELATIONSHIPS.items():
    fields = [relations[relation]['field'] \
        for relation in relations \
        if relations[relation]['model'] is Constituent]
    relationship_fields = {field: '{}_constituent_id'.format(field) \
        for field in fields}
    or_filters = [Q(**{'{}__isnull'.format(field): True}) \
        for field in fields]
    null_relations = reduce(lambda x, y: x | y, or_filters)
    filters = null_relations
    if constituent_id is not None:
        id_filters = [Q(**{field: constituent_id}) \
            for field in relationship_fields.values()]
        ids = reduce(lambda x, y: x & y, id_filters)
        filters = null_relations & ids
    objects = Model.objects.filter(filters)

    yield objects, relationship_fields