private com.google.protobuf.SingleFieldBuilderV3<
            com.google.cloud.texttospeech.v1.VoiceCloneParams,
            com.google.cloud.texttospeech.v1.VoiceCloneParams.Builder,
            com.google.cloud.texttospeech.v1.VoiceCloneParamsOrBuilder>
        getVoiceCloneFieldBuilder() {
      if (voiceCloneBuilder_ == null) {
        voiceCloneBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.cloud.texttospeech.v1.VoiceCloneParams,
                com.google.cloud.texttospeech.v1.VoiceCloneParams.Builder,
                com.google.cloud.texttospeech.v1.VoiceCloneParamsOrBuilder>(
                getVoiceClone(), getParentForChildren(), isClean());
        voiceClone_ = null;
      }
      return voiceCloneBuilder_;
    }
<pre>
Optional. The configuration for a voice clone. If
[VoiceCloneParams.voice_clone_key] is set, the service chooses the voice
clone matching the specified configuration.
</pre>

<code>
.google.cloud.texttospeech.v1.VoiceCloneParams voice_clone = 5 [(.google.api.field_behavior) = OPTIONAL];
</code>
java-texttospeech/proto-google-cloud-texttospeech-v1/src/main/java/com/google/cloud/texttospeech/v1/VoiceSelectionParams.java