def METHOD_NAME(self, local_path: str) -> list:
    # verify row count of fields are equal
    row_count = -1
    for k in self._buffer:
        if row_count < 0:
            row_count = len(self._buffer[k])
        elif row_count != len(self._buffer[k]):
            self._throw(
                "Column `{}` row count {} doesn't equal to the first column row count {}".format(
                    k, len(self._buffer[k]), row_count
                )
            )
    # output files
    if self._file_type == BulkFileType.NPY:
        return self._persist_npy(local_path)
    if self._file_type == BulkFileType.JSON_RB:
        return self._persist_json_rows(local_path)
    self._throw(f"Unsupported file tpye: {self._file_type}")
    return []