code: func (e *Engine) ImageBuildCachePrune(ctx context.Context, all bool) (uint64, error) {
  	r, err := e.client.BuildCachePrune(ctx, dockertypes.BuildCachePruneOptions{All: all})
  	if err != nil {
  		return 0, err
  	}
  	return r.SpaceReclaimed, nil
  }
docs: // ImageBuildCachePrune prune build cache