'Validates that the value is a valid list of foreign keys'

def isValidIDList(self, field_data, all_data):

    mod = self.rel.to
    try:
        pks = map(int, field_data.split(','))
    except ValueError:
        return
    objects = mod._default_manager.in_bulk(pks)
    if (len(objects) != len(pks)):
        badkeys = [k for k in pks if (k not in objects)]
        raise exceptions.ValidationError((ungettext('Please    enter    valid    %(self)s    IDs.    The    value    %(value)r    is    invalid.', 'Please    enter    valid    %(self)s    IDs.    The    values    %(value)r    are    invalid.', len(badkeys)) % {'self': self.verbose_name, 'value': (((len(badkeys) == 1) and badkeys[0]) or tuple(badkeys))}))
