docs: private static String getLongLiteral(LiteralTree literalTree, VisitorState state) {
      JCLiteral longLiteral = (JCLiteral) literalTree;
      CharSequence sourceFile = state.getSourceCode();
      if (sourceFile == null) {
        return null;
      }
      int start = longLiteral.getStartPosition();
      java.util.regex.Matcher matcher =
          LONG_LITERAL_PATTERN.matcher(sourceFile.subSequence(start, sourceFile.length()));
      if (matcher.lookingAt()) {
        return matcher.group();
      }
      return null;
    }