code: func (cps ComparablePrincipalSet) String() string {
  	buff := bytes.Buffer{}
  	buff.WriteString("[")
  	for i, cp := range cps {
  		buff.WriteString(cp.mspID)
  		buff.WriteString(".")
  		if cp.role != nil {
  			buff.WriteString(fmt.Sprintf("%v", cp.role.Role))
  		}
  		if cp.ou != nil {
  			buff.WriteString(fmt.Sprintf("%v", cp.ou.OrganizationalUnitIdentifier))
  		}
  		if i < len(cps)-1 {
  			buff.WriteString(", ")
  		}
  	}
  	buff.WriteString("]")
  	return buff.String()
  }
docs: // String returns a string representation of this ComparablePrincipalSet