code: def lookup_future_symbol(self, symbol):
          
  
          data = self._select_asset_by_symbol(self.futures_contracts, symbol)\
                     .execute().fetchone()
  
          # If no data found, raise an exception
          if not data:
              raise SymbolNotFound(symbol=symbol)
          return self.retrieve_asset(data['sid'])
docs: Lookup a future contract by symbol.
  
          Parameters
          ----------
          symbol : str
              The symbol of the desired contract.
  
          Returns
          -------
          future : Future
              The future contract referenced by ``symbol``.
  
          Raises
          ------
          SymbolNotFound
              Raised when no contract named 'symbol' is found.