docs: def _aggregate(self):
          """Helper method to aggregate RemoteTasks into single ssh session."""
          # pylint: disable=W0212
          nonremote = [t for t in self._tasks if not isinstance(t, RemoteTask)]
          remote = [t for t in self._tasks if isinstance(t, RemoteTask)]
  
          host_dict = defaultdict(list)
          for task in remote:
              host_dict[task.host].append(task)
  
          aggregated = []
          for task_group in host_dict.values():
              # Build up combined command
              combined_cmd = []
              for task in task_group:
                  if combined_cmd:
                      combined_cmd.append('&')
                  combined_cmd.append(' '.join(task._remote_command))
  
              # Now, generated aggregate task
              t0 = task_group[0] # pylint: disable=C0103
              task = RemoteTask(
                  t0.host, combined_cmd, t0._quiet, t0._return_output,
                  t0._kill_remote, t0._identity_file)
  
              aggregated.append(task)
  
          self._tasks = nonremote + aggregated