@java.lang.Override
  public void writeTo(com.google.protobuf.CodedOutputStream output) throws java.io.IOException {
    for (int i = 0; i < candidates_.size(); i++) {
      output.writeMessage(2, candidates_.get(i));
    }
    if (((bitField0_ & 0x00000002) != 0)) {
      output.writeMessage(3, getPromptFeedback());
    }
    if (((bitField0_ & 0x00000004) != 0)) {
      output.writeMessage(4, getUsageMetadata());
    }
    if (!com.google.protobuf.GeneratedMessageV3.isStringEmpty(modelVersion_)) {
      com.google.protobuf.GeneratedMessageV3.writeString(output, 11, modelVersion_);
    }
    if (((bitField0_ & 0x00000001) != 0)) {
      output.writeMessage(12, getCreateTime());
    }
    if (!com.google.protobuf.GeneratedMessageV3.isStringEmpty(responseId_)) {
      com.google.protobuf.GeneratedMessageV3.writeString(output, 13, responseId_);
    }
    getUnknownFields().writeTo(output);
  }
<pre>
Usage metadata about the response(s).
</pre>

<code>.google.cloud.vertexai.v1.GenerateContentResponse.UsageMetadata usage_metadata = 4;
</code>
java-vertexai/proto-google-cloud-vertexai-v1/src/main/java/com/google/cloud/vertexai/api/GenerateContentResponse.java