private void ensureReferenceSentencePairListsIsMutable() {
        if (!((bitField0_ & 0x00000001) != 0)) {
          referenceSentencePairLists_ =
              new java.util.ArrayList<
                  com.google.cloud.translate.v3.AdaptiveMtTranslateRequest
                      .ReferenceSentencePairList>(referenceSentencePairLists_);
          bitField0_ |= 0x00000001;
        }
      }
<pre>
Message of caller-provided reference configuration.
</pre>

Protobuf type {@code
google.cloud.translation.v3.AdaptiveMtTranslateRequest.ReferenceSentenceConfig}
java-translate/proto-google-cloud-translate-v3/src/main/java/com/google/cloud/translate/v3/AdaptiveMtTranslateRequest.java