code: def viewer_has_liked(self) -> Optional[bool]:
          
          if not self._context.is_logged_in:
              return None
          if 'likes' in self._node and 'viewer_has_liked' in self._node['likes']:
              return self._node['likes']['viewer_has_liked']
          return self._field('viewer_has_liked')
docs: Whether the viewer has liked the post, or None if not logged in.