code: func (p *Prefix) Contains(q *Prefix) bool {
  	if p.IP.To4() != nil {
  		return p.containsIPv4(q)
  	}
  	if p.IP.To16() != nil && p.IP.To4() == nil {
  		return p.containsIPv6(q)
  	}
  	return false
  }
docs: // Contains reports whether q is a subnetwork of p.