@java.lang.Override
  public com.google.protobuf.ByteString getResponseMimeTypeBytes() {
    java.lang.Object ref = responseMimeType_;
    if (ref instanceof java.lang.String) {
      com.google.protobuf.ByteString b =
          com.google.protobuf.ByteString.copyFromUtf8((java.lang.String) ref);
      responseMimeType_ = b;
      return b;
    } else {
      return (com.google.protobuf.ByteString) ref;
    }
  }
<pre>
Optional. Output response mimetype of the generated candidate text.
Supported mimetype:
- `text/plain`: (default) Text output.
- `application/json`: JSON response in the candidates.
The model needs to be prompted to output the appropriate response type,
otherwise the behavior is undefined.
This is a preview feature.
</pre>

<code>string response_mime_type = 13 [(.google.api.field_behavior) = OPTIONAL];</code>

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