@Override
  public BidiStreamingCallable<StreamingSynthesizeRequest, StreamingSynthesizeResponse>
      streamingSynthesizeCallable() {
    return streamingSynthesizeCallable;
  }
Constructs an instance of GrpcTextToSpeechStub, using the given settings. This is protected so
that it is easy to make a subclass, but otherwise, the static factory methods should be
preferred.
java-texttospeech/google-cloud-texttospeech/src/main/java/com/google/cloud/texttospeech/v1/stub/GrpcTextToSpeechStub.java