@java.lang.Override
  public void writeTo(com.google.protobuf.CodedOutputStream output) throws java.io.IOException {
    if (inputSourceCase_ == 1) {
      com.google.protobuf.GeneratedMessageV3.writeString(output, 1, inputSource_);
    }
    if (inputSourceCase_ == 5) {
      com.google.protobuf.GeneratedMessageV3.writeString(output, 5, inputSource_);
    }
    getUnknownFields().writeTo(output);
  }
<pre>
Markup for HD voices specifically. This field may not be used with any
other voices.
</pre>

<code>string markup = 5;</code>

@return The bytes for markup.
java-texttospeech/proto-google-cloud-texttospeech-v1/src/main/java/com/google/cloud/texttospeech/v1/StreamingSynthesisInput.java