@java.lang.Override
    public void writeTo(com.google.protobuf.CodedOutputStream output) throws java.io.IOException {
      if (rankingConfigCase_ == 1) {
        output.writeMessage(
            1,
            (com.google.cloud.vertexai.api.RagRetrievalConfig.Ranking.RankService) rankingConfig_);
      }
      if (rankingConfigCase_ == 3) {
        output.writeMessage(
            3, (com.google.cloud.vertexai.api.RagRetrievalConfig.Ranking.LlmRanker) rankingConfig_);
      }
      getUnknownFields().writeTo(output);
    }
<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