docs: private static String createMessage(List<?> missingOptions)
      {
          StringBuilder buf = new StringBuilder("Missing required option");
          buf.append(missingOptions.size() == 1 ? "" : "s");
          buf.append(": ");
  
          Iterator<?> it = missingOptions.iterator();
          while (it.hasNext())
          {
              buf.append(it.next());
              if (it.hasNext())
              {
                  buf.append(", ");
              }
          }
  
          return buf.toString();
      }