public Builder clearNextPageToken() {
      nextPageToken_ = getDefaultInstance().getNextPageToken();
      bitField0_ = (bitField0_ & ~0x00000002);
      onChanged();
      return this;
    }
<pre>
Optional.
</pre>

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

@return This builder for chaining.
java-translate/proto-google-cloud-translate-v3/src/main/java/com/google/cloud/translate/v3/ListAdaptiveMtSentencesResponse.java