@java.lang.Override
    public final Builder mergeUnknownFields(
        final com.google.protobuf.UnknownFieldSet unknownFields) {
      return super.mergeUnknownFields(unknownFields);
    }
<pre>
When available, billed audio seconds for the corresponding request.
</pre>

<code>.google.protobuf.Duration total_billed_duration = 6;</code>
java-speech/proto-google-cloud-speech-v2/src/main/java/com/google/cloud/speech/v2/RecognitionResponseMetadata.java