docs: function(sentences, options) {
      var voice = options.voice, callback = options.callback,
        iswrite = options.writetext;
      for (var i=0; i<sentences.length; i++) {
        speechList.push(sentences[i]);
      };
      try{
        tts(voice, iswrite, callback);
        return true;
      } catch(e) {
        throw new Error('error while speaking');
      }
    }