def get_prep_lookup(self, lookup_type, value):
        "Perform preliminary non-db specific lookup checks and conversions"
        if lookup_type == 'contains':
            return escape_ldap_filter(value)
        raise TypeError("ListField has invalid lookup: %s" % lookup_type)
dataset/ETHPy150Open django-ldapdb/django-ldapdb/ldapdb/models/fields.py/ListField.get_prep_lookup/original