public Builder mergeRankService(
          com.google.cloud.vertexai.api.RagRetrievalConfig.Ranking.RankService value) {
        if (rankServiceBuilder_ == null) {
          if (rankingConfigCase_ == 1
              && rankingConfig_
                  != com.google.cloud.vertexai.api.RagRetrievalConfig.Ranking.RankService
                      .getDefaultInstance()) {
            rankingConfig_ =
                com.google.cloud.vertexai.api.RagRetrievalConfig.Ranking.RankService.newBuilder(
                        (com.google.cloud.vertexai.api.RagRetrievalConfig.Ranking.RankService)
                            rankingConfig_)
                    .mergeFrom(value)
                    .buildPartial();
          } else {
            rankingConfig_ = value;
          }
          onChanged();
        } else {
          if (rankingConfigCase_ == 1) {
            rankServiceBuilder_.mergeFrom(value);
          } else {
            rankServiceBuilder_.setMessage(value);
          }
        }
        rankingConfigCase_ = 1;
        return this;
      }
<pre>
Optional. Config for Rank Service.
</pre>

<code>
.google.cloud.vertexai.v1.RagRetrievalConfig.Ranking.RankService rank_service = 1 [(.google.api.field_behavior) = OPTIONAL];
</code>
java-vertexai/proto-google-cloud-vertexai-v1/src/main/java/com/google/cloud/vertexai/api/RagRetrievalConfig.java