private com.google.protobuf.SingleFieldBuilderV3<
              com.google.cloud.vertexai.api.RagRetrievalConfig.Ranking.LlmRanker,
              com.google.cloud.vertexai.api.RagRetrievalConfig.Ranking.LlmRanker.Builder,
              com.google.cloud.vertexai.api.RagRetrievalConfig.Ranking.LlmRankerOrBuilder>
          getLlmRankerFieldBuilder() {
        if (llmRankerBuilder_ == null) {
          if (!(rankingConfigCase_ == 3)) {
            rankingConfig_ =
                com.google.cloud.vertexai.api.RagRetrievalConfig.Ranking.LlmRanker
                    .getDefaultInstance();
          }
          llmRankerBuilder_ =
              new com.google.protobuf.SingleFieldBuilderV3<
                  com.google.cloud.vertexai.api.RagRetrievalConfig.Ranking.LlmRanker,
                  com.google.cloud.vertexai.api.RagRetrievalConfig.Ranking.LlmRanker.Builder,
                  com.google.cloud.vertexai.api.RagRetrievalConfig.Ranking.LlmRankerOrBuilder>(
                  (com.google.cloud.vertexai.api.RagRetrievalConfig.Ranking.LlmRanker)
                      rankingConfig_,
                  getParentForChildren(),
                  isClean());
          rankingConfig_ = null;
        }
        rankingConfigCase_ = 3;
        onChanged();
        return llmRankerBuilder_;
      }
<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