code: func (h *Handle) LinkSetMaster(link Link, master *Bridge) error {
  	index := 0
  	if master != nil {
  		masterBase := master.Attrs()
  		h.ensureIndex(masterBase)
  		index = masterBase.Index
  	}
  	if index <= 0 {
  		return fmt.Errorf("Device does not exist")
  	}
  	return h.LinkSetMasterByIndex(link, index)
  }
docs: // LinkSetMaster sets the master of the link device.
  // Equivalent to: `ip link set $link master $master`