For the given root symbol, find the contract that is considered active
        on a specific date at a specific offset.

def _get_active_contract_at_offset(self, root_symbol, dt, offset):
        """
        For the given root symbol, find the contract that is considered active
        on a specific date at a specific offset.
        """
        oc = self.asset_finder.get_ordered_contracts(root_symbol)
        session = self.trading_calendar.minute_to_session_label(dt)
        front = oc.contract_before_auto_close(session.value)
        back = oc.contract_at_offset(front, 1, dt.value)
        if back is None:
            return front
        primary = self._active_contract(oc, front, back, session)
        return oc.contract_at_offset(primary, offset, session.value)