@java.lang.Override
  protected Builder newBuilderForType(com.google.protobuf.GeneratedMessageV3.BuilderParent parent) {
    Builder builder = new Builder(parent);
    return builder;
  }
<pre>
Optional. Recommended.
[BCP-47](https://www.rfc-editor.org/rfc/bcp/bcp47.txt) language tag.
If not specified, the API will return all supported voices.
If specified, the ListVoices call will only return voices that can be used
to synthesize this language_code. For example, if you specify `"en-NZ"`,
all `"en-NZ"` voices will be returned. If you specify `"no"`, both
`"no-&#92;*"` (Norwegian) and `"nb-&#92;*"` (Norwegian Bokmal) voices will be
returned.
</pre>

<code>string language_code = 1 [(.google.api.field_behavior) = OPTIONAL];</code>

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