Returns image order number. It is calculated as (number+1) of images
        attached to the same content_object whose order is greater
        (if 'reverse_ordering' is True) or lesser (if 'reverse_ordering' is
        False) than image's order.

def get_order_in_album(self, reversed_ordering=True):
        ''' Returns image order number. It is calculated as (number+1) of images
        attached to the same content_object whose order is greater
        (if 'reverse_ordering' is True) or lesser (if 'reverse_ordering' is
        False) than image's order.
        '''
        lookup = 'order__gt' if reversed_ordering else 'order__lt'
        return self.__class__.objects.\
                        for_model(self.content_object, self.content_type).\
                        filter(**{lookup: self.order}).count() + 1