code: public void addLanguage( QueryParser languageParser ) {
          CheckArg.isNotNull(languageParser, "languageParser");
          this.parsers.put(languageParser.getLanguage().trim().toLowerCase(), languageParser);
      }
docs: Add a language to this engine by supplying its parser.
  
  @param languageParser the query parser for the language
  @throws IllegalArgumentException if the language parser is null