(row)
return row['schema_name'], row['query_signature']
:param row: a normalized row from events_statements_summary_by_digest
    :return: a tuple uniquely identifying this row
:param row: a normalized row from events_statements_summary_by_digest
    :return: a tuple uniquely identifying this row
: param row : a normalized row from events_statements_summary_by_digest : return : a tuple uniquely identifying this row
def _row_key(row):
    """
    :param row: a normalized row from events_statements_summary_by_digest
    :return: a tuple uniquely identifying this row
    """
    return row['schema_name'], row['query_signature']
def _row_key ( row ) : return row [ 'schema_name' ] , row [ 'query_signature' ]