def METHOD_NAME(self):
    name_accu = collections.defaultdict(list)
    for ie in self.ies:
        name_accu[ie.IE_NAME.lower()].append(type(ie).__name__)
    for (ie_name, ie_list) in name_accu.items():
        self.assertEqual(
            len(ie_list), 1,
            'Multiple extractors with the same IE_NAME "%s" (%s)' % (ie_name, ', '.join(ie_list)))