code: def running_time(self):
          
          if not self.is_done():
              raise ValueError("Cannot get running time for a program that isn't completed.")
          try:
              running_time = float(self._raw['running_time'].split()[0])
          except (ValueError, KeyError, IndexError):
              raise UnknownApiError(str(self._raw))
          return running_time
docs: For how long was the job running?
          :return: Running time, seconds
          :rtype: Optional[float]