def _normalize_rename_handler(self, mapping, schema, field):
        """ {'oneof': [
                {'type': 'callable'},
                {'type': 'list',
                 'schema': {'oneof': [{'type': 'callable'},
                                      {'type': 'string'}]}},
                {'type': 'string'}
                ]} """
        if 'rename_handler' not in schema[field]:
            return
        new_name = self.__normalize_coerce(
            schema[field]['rename_handler'], field, field,
            False, errors.RENAMING_FAILED)
        if new_name != field:
            mapping[new_name] = mapping[field]
            del mapping[field]
{'oneof': [
                {'type': 'callable'},
                {'type': 'list',
                 'schema': {'oneof': [{'type': 'callable'},
                                      {'type': 'string'}]}},
                {'type': 'string'}
                ]}