code: func (engine *DockerStatsEngine) removeContainer(dockerID string) {
  	engine.lock.Lock()
  	defer engine.lock.Unlock()
  
  	// Make sure that this container belongs to a task.
  	task, err := engine.resolver.ResolveTask(dockerID)
  	if err != nil {
  		seelog.Debugf("Could not map container to task, ignoring, err: %v, id: %s", err, dockerID)
  		return
  	}
  
  	_, taskExists := engine.tasksToContainers[task.Arn]
  	if !taskExists {
  		seelog.Debugf("Container not being watched, id: %s", dockerID)
  		return
  	}
  
  	// task arn exists in map.
  	container, containerExists := engine.tasksToContainers[task.Arn][dockerID]
  	if !containerExists {
  		// container arn does not exist in map.
  		seelog.Debugf("Container not being watched, id: %s", dockerID)
  		return
  	}
  
  	engine.doRemoveContainerUnsafe(container, task.Arn)
  }
docs: // removeContainer deletes the container from the map of containers being watched.
  // It also stops the periodic usage data collection for the container.