code: public static Kidnummer getKidnummer(String kidnummer) throws IllegalArgumentException {
          validateSyntax(kidnummer);
          validateChecksum(kidnummer);
          return new Kidnummer(kidnummer);
      }
docs: Returns an object that represents a Kidnummer.
  
  @param kidnummer A String containing a Kidnummer
  @return A Kidnummer instance
  @throws IllegalArgumentException thrown if String contains an invalid Kidnummer