public Builder clearCustomVoice() {
      bitField0_ = (bitField0_ & ~0x00000008);
      customVoice_ = null;
      if (customVoiceBuilder_ != null) {
        customVoiceBuilder_.dispose();
        customVoiceBuilder_ = null;
      }
      onChanged();
      return this;
    }
<pre>
The configuration for a custom voice. If [CustomVoiceParams.model] is set,
the service will choose the custom voice matching the specified
configuration.
</pre>

<code>.google.cloud.texttospeech.v1beta1.CustomVoiceParams custom_voice = 4;</code>
java-texttospeech/proto-google-cloud-texttospeech-v1beta1/src/main/java/com/google/cloud/texttospeech/v1beta1/VoiceSelectionParams.java