def delete_docs(self, ids, step=None):
        '''delete a list of docs in bulk.'''
        index_name = self._index
        doc_type = self._doc_type
        step = step or self.step

        def _get_bulk(_id):
            if self._host_major_ver >= 7:
                doc = {
                    '_op_type': 'delete',
                    "_index": index_name,
                    "_id": _id
                }
            else:
                doc = {
                    '_op_type': 'delete',
                    "_index": index_name,
                    "_type": doc_type,
                    "_id": _id
                }
            return doc
        actions = (_get_bulk(_id) for _id in ids)
        return helpers.bulk(self._es, actions, chunk_size=step, stats_only=True, raise_on_error=False)