private com.google.protobuf.SingleFieldBuilderV3<
            com.google.protobuf.Value,
            com.google.protobuf.Value.Builder,
            com.google.protobuf.ValueOrBuilder>
        getMetadataFieldBuilder() {
      if (metadataBuilder_ == null) {
        metadataBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.protobuf.Value,
                com.google.protobuf.Value.Builder,
                com.google.protobuf.ValueOrBuilder>(
                getMetadata(), getParentForChildren(), isClean());
        metadata_ = null;
      }
      return metadataBuilder_;
    }
<pre>
Output only. Request-level metadata returned by the model. The metadata
type will be dependent upon the model implementation.
</pre>

<code>.google.protobuf.Value metadata = 6 [(.google.api.field_behavior) = OUTPUT_ONLY];
</code>
java-vertexai/proto-google-cloud-vertexai-v1/src/main/java/com/google/cloud/vertexai/api/PredictResponse.java