code: func (cps ComparablePrincipalSets) ToPrincipalSets() policies.PrincipalSets {
  	var res policies.PrincipalSets
  	for _, cp := range cps {
  		res = append(res, cp.ToPrincipalSet())
  	}
  	return res
  }
docs: // ToPrincipalSets converts this ComparablePrincipalSets to a PrincipalSets