code: def get_last_traded_dt(self, asset, dt):
          
          try:
              return self.frames['close'].loc[:, asset.sid].last_valid_index()
          except IndexError:
              return NaT
docs: Parameters
          ----------
          asset : zipline.asset.Asset
              The asset identifier.
          dt : datetime64-like
              Midnight of the day for which data is requested.
  
          Returns
          -------
          pd.Timestamp : The last know dt for the asset and dt;
                         NaT if no trade is found before the given dt.