code: func IsRFC5737(na *wire.NetAddress) bool {
  	for _, rfc := range rfc5737Net {
  		if rfc.Contains(na.IP) {
  			return true
  		}
  	}
  
  	return false
  }
docs: // IsRFC5737 returns whether or not the passed address is part of the IPv4
  // documentation address space as defined by RFC5737 (192.0.2.0/24,
  // 198.51.100.0/24, 203.0.113.0/24)