Internal method that returns a dataframe containing history bars
        of daily frequency for the given sids.

def _get_history_daily_window(self,
                                  assets,
                                  end_dt,
                                  bar_count,
                                  field_to_use,
                                  data_frequency):
        """
        Internal method that returns a dataframe containing history bars
        of daily frequency for the given sids.
        """
        session = self.trading_calendar.minute_to_session_label(end_dt)
        days_for_window = self._get_days_for_window(session, bar_count)

        if len(assets) == 0:
            return pd.DataFrame(None,
                                index=days_for_window,
                                columns=None)

        data = self._get_history_daily_window_data(
            assets, days_for_window, end_dt, field_to_use, data_frequency
        )
        return pd.DataFrame(
            data,
            index=days_for_window,
            columns=assets
        )