code: func (w RefSet) Has(ref string) bool {
  	for prefix, wrp := range w.byPrefix {
  		nsPrefix := prefix + "/"
  		if strings.HasPrefix(ref, nsPrefix) && wrp.hasRef(ref) {
  			return true
  		}
  	}
  
  	return false
  }
docs: // Has checks if a specific ref is in this set.