code: public StreamResponse startStream(String uuid, String streamUrl, int loop) throws IOException, NexmoClientException {
          return streams.put(new StreamRequest(uuid, streamUrl, loop));
      }
docs: Stream audio to an ongoing call.
  
  @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 streamUrl A URL of an audio file in MP3 or 16-bit WAV format, to be streamed to the call.
  @param loop      The number of times to repeat the audio. The default value is {@code 1}, or you can use
  {@code 0} to indicate that the audio should be repeated indefinitely.
  
  @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.