public com.google.protobuf.ByteString getNextPageTokenBytes() {
      java.lang.Object ref = nextPageToken_;
      if (ref instanceof String) {
        com.google.protobuf.ByteString b =
            com.google.protobuf.ByteString.copyFromUtf8((java.lang.String) ref);
        nextPageToken_ = b;
        return b;
      } else {
        return (com.google.protobuf.ByteString) ref;
      }
    }
<pre>
Optional. A token to retrieve a page of results. Pass this value in the
[ListAdaptiveMtDatasetsRequest.page_token] field in the subsequent call to
`ListAdaptiveMtDatasets` method to retrieve the next page of results.
</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/ListAdaptiveMtDatasetsResponse.java