docs: function(mathml, id, constructor, onSpeech, time) {
        var messageID = Explorer.AddMessage();
        setTimeout(function() {
          var speechGenerator = new constructor();
          var math = document.getElementById(id);
          var dummy = new sre.DummyWalker(
              math, speechGenerator, Explorer.highlighter, mathml);
          var speech = dummy.speech();
          if (speech) {
            onSpeech(math, speech);
          }
          Explorer.RemoveMessage(messageID);
        }, time);
      }