public java.lang.String getNextPageToken() {
      java.lang.Object ref = nextPageToken_;
      if (!(ref instanceof java.lang.String)) {
        com.google.protobuf.ByteString bs = (com.google.protobuf.ByteString) ref;
        java.lang.String s = bs.toStringUtf8();
        nextPageToken_ = s;
        return s;
      } else {
        return (java.lang.String) ref;
      }
    }
<pre>
Token to retrieve the next page of results, or empty if there are no more
results in the list.
</pre>

<code>string next_page_token = 2;</code>

@return The nextPageToken.
java-vision/proto-google-cloud-vision-v1p4beta1/src/main/java/com/google/cloud/vision/v1p4beta1/ListProductSetsResponse.java