撤单

    :param order: 需要撤销的order对象
    :type order: :class:`~Order` object

def cancel_order(order):
    """
    撤单

    :param order: 需要撤销的order对象
    :type order: :class:`~Order` object
    """
    env = Environment.get_instance()
    if env.can_cancel_order(order):
        env.broker.cancel_order(order)
    return order