private com.google.protobuf.SingleFieldBuilderV3<
            com.google.cloud.vertexai.api.ExplanationMetadata,
            com.google.cloud.vertexai.api.ExplanationMetadata.Builder,
            com.google.cloud.vertexai.api.ExplanationMetadataOrBuilder>
        getMetadataFieldBuilder() {
      if (metadataBuilder_ == null) {
        metadataBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.cloud.vertexai.api.ExplanationMetadata,
                com.google.cloud.vertexai.api.ExplanationMetadata.Builder,
                com.google.cloud.vertexai.api.ExplanationMetadataOrBuilder>(
                getMetadata(), getParentForChildren(), isClean());
        metadata_ = null;
      }
      return metadataBuilder_;
    }
<pre>
Optional. Metadata describing the Model's input and output for explanation.
</pre>

<code>
.google.cloud.vertexai.v1.ExplanationMetadata metadata = 2 [(.google.api.field_behavior) = OPTIONAL];
</code>
java-vertexai/proto-google-cloud-vertexai-v1/src/main/java/com/google/cloud/vertexai/api/ExplanationSpec.java