code: func getSandboxPortMapInfo(sb libnetwork.Sandbox) nat.PortMap {
  	pm := nat.PortMap{}
  	if sb == nil {
  		return pm
  	}
  
  	for _, ep := range sb.Endpoints() {
  		pm, _ = getEndpointPortMapInfo(ep)
  		if len(pm) > 0 {
  			break
  		}
  	}
  	return pm
  }
docs: // getSandboxPortMapInfo retrieves the current port-mapping programmed for the given sandbox