code: func (c *Corpus) PermanodeAnyTime(pn blob.Ref) (t time.Time, ok bool) {
  	if t, ok := c.PermanodeTime(pn); ok {
  		return t, ok
  	}
  	return c.PermanodeModtime(pn)
  }
docs: // PermanodeAnyTime returns the time that best qualifies the permanode.
  // It tries content-specific times first, the permanode modtime otherwise.