'If the operation succeeded, return its result.  If it failed,
re-raise its exception.'

def result(self, timeout=None):

    self._clear_tb_log()
    if (self._result is not None):
        return self._result
    if (self._exc_info is not None):
        raise_exc_info(self._exc_info)
    self._check_done()
    return self._result
