public Builder setLlmRanker(
          com.google.cloud.vertexai.api.RagRetrievalConfig.Ranking.LlmRanker.Builder
              builderForValue) {
        if (llmRankerBuilder_ == null) {
          rankingConfig_ = builderForValue.build();
          onChanged();
        } else {
          llmRankerBuilder_.setMessage(builderForValue.build());
        }
        rankingConfigCase_ = 3;
        return this;
      }
<pre>
Optional. Config for LlmRanker.
</pre>

<code>
.google.cloud.vertexai.v1.RagRetrievalConfig.Ranking.LlmRanker llm_ranker = 3 [(.google.api.field_behavior) = OPTIONAL];
</code>
java-vertexai/proto-google-cloud-vertexai-v1/src/main/java/com/google/cloud/vertexai/api/RagRetrievalConfig.java