docs: public Optional<Object> lookupLexer(PyGateway gateway, String alias) {
          Object result = lexerCache.get(alias);
  
          if (result == null) {
              result = evalLookupLexer(gateway, alias, NULL);
              lexerCache.put(alias, result);
          }
  
          if (result == NULL) {
              return Optional.absent();
          } else {
              return Optional.of(result);
          }
      }