High-level method to do "more like this".

        Its exact implementation can vary.

def mlt(self, _id):
        '''
        High-level method to do "more like this".

        Its exact implementation can vary.
        '''
        query = {
            'query': {'more_like_this': {
                      'like': {'_id': _id},
                      'min_term_freq': 1,
                      'min_doc_freq': 1,
             }}
        }
        if es_version[0] <= 1:
            mlt = query['query']['more_like_this']
            mlt['ids'] = [_id]
            del mlt['like']
        return self._search(query)