code: def last_date_in_output_for_sid(self, sid):
          
          sizes_path = "{0}/close/meta/sizes".format(self.sidpath(sid))
          if not os.path.exists(sizes_path):
              return pd.NaT
          with open(sizes_path, mode='r') as f:
              sizes = f.read()
          data = json.loads(sizes)
          # use integer division so that the result is an int
          # for pandas index later https://github.com/pandas-dev/pandas/blob/master/pandas/tseries/base.py#L247 # noqa
          num_days = data['shape'][0] // self._minutes_per_day
          if num_days == 0:
              # empty container
              return pd.NaT
          return self._session_labels[num_days - 1]
docs: Parameters
          ----------
          sid : int
              Asset identifier.
  
          Returns
          -------
          out : pd.Timestamp
              The midnight of the last date written in to the output for the
              given sid.