code: func (p *PortBinding) String() string {
  	ret := fmt.Sprintf("%s/", p.Proto)
  	if p.IP != nil {
  		ret += p.IP.String()
  	}
  	ret = fmt.Sprintf("%s:%d/", ret, p.Port)
  	if p.HostIP != nil {
  		ret += p.HostIP.String()
  	}
  	ret = fmt.Sprintf("%s:%d", ret, p.HostPort)
  	return ret
  }
docs: // String returns the PortBinding structure in string form