default boolean onlyRaisesNotImplementedError() {
    final PyAstStatement[] statements = getStatementList().getStatements();
    return statements.length == 1 && isRaiseNotImplementedError(statements[0]) ||
           statements.length == 2 && PyUtilCore.isStringLiteral(statements[0]) && isRaiseNotImplementedError(statements[1]);
  }
default boolean onlyRaisesNotImplementedError()