public Builder setMetadata(com.google.protobuf.Value value) {
      if (metadataBuilder_ == null) {
        if (value == null) {
          throw new NullPointerException();
        }
        metadata_ = value;
      } else {
        metadataBuilder_.setMessage(value);
      }
      bitField0_ |= 0x00000020;
      onChanged();
      return this;
    }
<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