'Mark the order with order_id as \'held\'. Held is functionally similar
to \'open\'. When a fill (full or partial) arrives, the status
will automatically change back to open/filled as necessary.'

def hold(self, order_id, reason=''):

    if (order_id not in self.orders):
        return
    cur_order = self.orders[order_id]
    if cur_order.open:
        if (cur_order in self.new_orders):
            self.new_orders.remove(cur_order)
        cur_order.hold(reason=reason)
        cur_order.dt = self.current_dt
        self.new_orders.append(cur_order)
