code: public TalkResponse startTalk(String uuid, String text) throws IOException, NexmoClientException {
          return talk.put(new TalkRequest(uuid, text));
      }
docs: Send a synthesized speech message to an ongoing call.
  <p>
  The message will only play once, spoken with the default voice of Kimberly.
  
  @param uuid The UUID of the call, obtained from the object returned by {@link #createCall(Call)}. This value can
  be obtained with {@link CallEvent#getUuid()}
  @param text The message to be spoken to the call participants.
  
  @return The data returned from the Voice API.
  
  @throws IOException          if a network error occurred contacting the Nexmo Voice API.
  @throws NexmoClientException if there was a problem with the Nexmo request or response objects.