@java.lang.Override
      public void writeTo(com.google.protobuf.CodedOutputStream output) throws java.io.IOException {
        if (((bitField0_ & 0x00000001) != 0)) {
          com.google.protobuf.GeneratedMessageV3.writeString(output, 1, modelName_);
        }
        getUnknownFields().writeTo(output);
      }
<pre>
Optional. The model name used for ranking.
Format: `gemini-1.5-pro`
</pre>

<code>optional string model_name = 1 [(.google.api.field_behavior) = OPTIONAL];</code>

@return The bytes for modelName.
java-vertexai/proto-google-cloud-vertexai-v1/src/main/java/com/google/cloud/vertexai/api/RagRetrievalConfig.java