code: public DefaultStreamingEndpoint languages(List<String> languages) {
      addPostParameter(Constants.LANGUAGE_PARAM, Joiner.on(',').join(languages));
      return this;
    }
docs: Filter for public tweets on these languages.
  
  @param languages
  Valid BCP 47 (http://tools.ietf.org/html/bcp47) language identifiers,
  and may represent any of the languages listed on Twitter's advanced search page
  (https://twitter.com/search-advanced), or "und" if no language could be detected.
  These strings should NOT be url-encoded.
  @return this