@java.lang.Override
  protected Builder newBuilderForType(com.google.protobuf.GeneratedMessageV3.BuilderParent parent) {
    Builder builder = new Builder(parent);
    return builder;
  }
<pre>
Optional.
</pre>

<code>string next_page_token = 2 [(.google.api.field_behavior) = OPTIONAL];</code>

@return The bytes for nextPageToken.
java-translate/proto-google-cloud-translate-v3/src/main/java/com/google/cloud/translate/v3/ListAdaptiveMtSentencesResponse.java