docs: @Override
    public String getNext() {
      try {
        int a;
        while ((a = lexer.yylex()) == CHTBLexer.IGNORE) {
          //System.err.println("#ignored: " + lexer.match());
        }
        if (a == CHTBLexer.YYEOF) {
          return null;
        } else {
          //System.err.println("#matched: " + lexer.match());
          return lexer.match();
        }
      } catch (IOException ioe) {
        // do nothing, return null
      }
      return null;
    }