Get the latest day on or before ``dt`` in which ``asset`` traded.

        If there are no trades on or before ``dt``, returns ``pd.NaT``.

        Parameters
        ----------
        asset : zipline.asset.Asset
            The asset for which to get the last traded day.
        dt : pd.Timestamp
            The dt at which to start searching for the last traded day.

        Returns
        -------
        last_traded : pd.Timestamp
            The day of the last trade for the given asset, using the
            input dt as a vantage point.

def get_last_traded_dt(self, asset, dt):
        """
        Get the latest day on or before ``dt`` in which ``asset`` traded.

        If there are no trades on or before ``dt``, returns ``pd.NaT``.

        Parameters
        ----------
        asset : zipline.asset.Asset
            The asset for which to get the last traded day.
        dt : pd.Timestamp
            The dt at which to start searching for the last traded day.

        Returns
        -------
        last_traded : pd.Timestamp
            The day of the last trade for the given asset, using the
            input dt as a vantage point.
        """
        country_code = self._country_code_for_assets([asset.sid])
        return self._readers[country_code].get_last_traded_dt(asset, dt)