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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def process_order(self, order):
 """Keep track of an order that was placed. Parameters order : zp.Order The order to record. """

        try:
            dt_orders = self._orders_by_modified[order.dt]
        except KeyError:
            self._orders_by_modified[order.dt] = OrderedDict([
                (order.id, order),
            ])
            self._orders_by_id[order.id] = order
        else:
            self._orders_by_id[order.id] = dt_orders[order.id] = order
            # to preserve the order of the orders by modified date
            move_to_end(dt_orders, order.id, last=True)

        move_to_end(self._orders_by_id, order.id, last=True)