code: def notify_thread_not_alive(self, thread_id, use_lock=True):
          
          if self.writer is None:
              return
  
          with self._lock_running_thread_ids if use_lock else NULL:
              if not self._enable_thread_notifications:
                  return
  
              thread = self._running_thread_ids.pop(thread_id, None)
              if thread is None:
                  return
  
              was_notified = thread.additional_info.pydev_notify_kill
              if not was_notified:
                  thread.additional_info.pydev_notify_kill = True
  
          self.writer.add_command(self.cmd_factory.make_thread_killed_message(thread_id))
docs: if thread is not alive, cancel trace_dispatch processing