code: func (vm VirtualMachine) NicByNetworkID(networkID UUID) *Nic {
  	for _, nic := range vm.Nic {
  		if nic.NetworkID.Equal(networkID) {
  			n := nic
  			n.VirtualMachineID = vm.ID
  			return &n
  		}
  	}
  	return nil
  }
docs: // NicByNetworkID returns the corresponding interface based on the given NetworkID
  //
  // A VM cannot be connected twice to a same network.