'When filtering against this relation, return the field on the remote
model against which the filtering should happen.'

@property
def target_field(self):

    target_fields = self.get_path_info()[(-1)].target_fields
    if (len(target_fields) > 1):
        raise exceptions.FieldError("Can't    use    target_field    for    multicolumn    relations.")
    return target_fields[0]
