def METHOD_NAME(definition: OvalDefinition) -> Set[str]:
    all_urls = set()
    definition_metadata = definition.getMetadata().element
    for child in definition_metadata:
        if child.tag.endswith("reference"):
            all_urls.add(child.get("ref_url"))
        if child.tag.endswith("advisory"):
            for grandchild in child:
                if grandchild.tag.endswith("ref"):
                    all_urls.add(grandchild.text)
                if grandchild.get("href"):
                    all_urls.add(grandchild.get("href"))
            break
    return all_urls