code: def add_stock_to_class(self, assetclass_id: int, symbol: str):
          
          assert isinstance(symbol, str)
          assert isinstance(assetclass_id, int)
  
          item = AssetClassStock()
          item.assetclassid = assetclass_id
          item.symbol = symbol
  
          session = self.open_session()
          session.add(item)
          self.save()
  
          return item
docs: Add a stock link to an asset class