List of all lowercased users that are tagged in the Post.

def tagged_users(self) -> List[str]:
        """List of all lowercased users that are tagged in the Post."""
        try:
            return [edge['node']['user']['username'].lower() for edge in self._field('edge_media_to_tagged_user',
                                                                                     'edges')]
        except KeyError:
            return []