def history(self, bar_count, frequency, field, ffill=True):
        """DEPRECATED: use ``data.history`` instead.
        """
        warnings.warn(
            "The `history` method is deprecated.  Use `data.history` instead.",
            category=ZiplineDeprecationWarning,
            stacklevel=4
        )

        return self.get_history_window(
            bar_count,
            frequency,
            self._calculate_universe(),
            field,
            ffill
        )
DEPRECATED: use ``data.history`` instead.