docs: public void addPhoneNumber(String newPhoneNumber) {
          if (newPhoneNumber==null || newPhoneNumber.trim().length()==0) {
              return;
          }
  
          if (phoneNumbers == null) {
              phoneNumbers = new ArrayList<>(1);
          }
          for (PhoneNumber phoneNumber : phoneNumbers) {
              if (phoneNumber.value.equals(newPhoneNumber) && phoneNumber.getType() == null) {
                  throw new IllegalArgumentException("Already contains phoneNumber " + newPhoneNumber);
              }
          }
  
          PhoneNumber number = new PhoneNumber();
          number.setValue(newPhoneNumber);
          phoneNumbers.add(number);
      }