public com.google.cloud.vertexai.api.CitationMetadataOrBuilder getCitationMetadataOrBuilder() {
      if (citationMetadataBuilder_ != null) {
        return citationMetadataBuilder_.getMessageOrBuilder();
      } else {
        return citationMetadata_ == null
            ? com.google.cloud.vertexai.api.CitationMetadata.getDefaultInstance()
            : citationMetadata_;
      }
    }
<pre>
Output only. Source attribution of the generated content.
</pre>

<code>
.google.cloud.vertexai.v1.CitationMetadata citation_metadata = 6 [(.google.api.field_behavior) = OUTPUT_ONLY];
</code>
java-vertexai/proto-google-cloud-vertexai-v1/src/main/java/com/google/cloud/vertexai/api/Candidate.java