code: func backendsListEqual(a, b []*compute.Backend) bool {
  	if len(a) != len(b) {
  		return false
  	}
  	if len(a) == 0 {
  		return true
  	}
  
  	aSet := sets.NewString()
  	for _, v := range a {
  		aSet.Insert(v.Group)
  	}
  	bSet := sets.NewString()
  	for _, v := range b {
  		bSet.Insert(v.Group)
  	}
  
  	return aSet.Equal(bSet)
  }
docs: // backendsListEqual asserts that backend lists are equal by instance group link only