code: func (d *naiveDiffDriverWithApply) ApplyDiff(id, parent string, diff io.Reader) (int64, error) {
  	b, err := d.applyDiff.ApplyDiff(id, parent, diff)
  	if err == ErrApplyDiffFallback {
  		return d.Driver.ApplyDiff(id, parent, diff)
  	}
  	return b, err
  }
docs: // ApplyDiff creates a diff layer with either the NaiveDiffDriver or with a fallback.