code: func (c *ContainerServer) GetContainerTopLayerID(containerID string) (string, error) {
  	ctr, err := c.GetStorageContainer(containerID)
  	if err != nil {
  		return "", err
  	}
  	return ctr.LayerID, nil
  }
docs: // GetContainerTopLayerID gets the ID of the top layer of the given container