code: def add_asset(self, ):
          
          i = self.asset_treev.currentIndex()
          item = i.internalPointer()
          if item:
              asset = item.internal_data()
              if not isinstance(asset, djadapter.models.Asset):
                  return
              if self._shot:
                  self._shot.assets.add(asset)
              else:
                  self._asset.assets.add(asset)
              self.assets.append(asset)
              item.set_parent(None)
docs: Add a asset and store it in the self.assets
  
          :returns: None
          :rtype: None
          :raises: None