attrs is an dictionary with 9 initial entries: form for 'form', extra for 'extra', can_order for 'can_order',
attrs = { 'form' : form , 'extra' : extra , 'can_order' : can_order , 'can_delete' : can_delete , 'min_num' : min_num , 'max_num' : max_num , 'absolute_max' : absolute_max , 'validate_min' : validate_min , 'validate_max' : validate_max }