old_contents: from typing import Union
  from typing import Optional
  
  from pricewars.models.PricewarsObject import PricewarsObject
  from pricewars.models import Product
  
  
  class Order(PricewarsObject):
      def __init__(self, price: float, stock: int, product: Union[Product, dict], left_in_stock: Optional[int] = None):
          self.price = price
          self.stock = stock
          self.left_in_stock = left_in_stock
          if type(product) == dict:
              self.product = Product.from_dict(product)
          else:
              self.product = product
  
new_contents: from typing import Union
  from typing import Optional
  
  from pricewars.models.PricewarsObject import PricewarsObject
  from pricewars.models import Product
  
  
  class Order(PricewarsObject):
      def __init__(self, billing_amount: float, stock: int, product: Union[Product, dict],
                   left_in_stock: Optional[int] = None):
          self.billing_amount = billing_amount
          self.stock = stock
          self.left_in_stock = left_in_stock
          if type(product) == dict:
              self.product = Product.from_dict(product)
          else:
              self.product = product
  
subject: rename order entry from price to billing_amount