docs: def _poll(self) -> None:
          """Check the status of the wrapped running subprocess.
  
          Note:
              This should only be called on currently-running tasks.
  
          """
          if self._subprocess is None:
              raise SublemonLifetimeError(
                  'Attempted to poll a non-active subprocess')
          elif self._subprocess.returncode is not None:
              self._exit_code = self._subprocess.returncode
              self._done_running_evt.set()
              self._server._running_set.remove(self)
              self._server._sem.release()