docs: public static SubstitutedLine parseHeadersLine(String commandLine, final CommandLineParser.CallbackHandler handler, final CommandContext ctx) throws CommandFormatException {
          if (commandLine == null) {
              return null;
          }
          final ParsingStateCallbackHandler callbackHandler = getCallbackHandler(handler);
          return StateParser.parseLine(commandLine, callbackHandler, HeaderListState.INSTANCE, ctx);
      }