code: def add_item(cls, item, **kwargs):
          
          kwargs['_return_http_data_only'] = True
          if kwargs.get('async'):
              return cls._add_item_with_http_info(item, **kwargs)
          else:
              (data) = cls._add_item_with_http_info(item, **kwargs)
              return data
docs: Add item.
  
          Add new item to the shopping cart.
          This method makes a synchronous HTTP request by default. To make an
          asynchronous HTTP request, please pass async=True
          >>> thread = api.add_item(item, async=True)
          >>> result = thread.get()
  
          :param async bool
          :param LineItem item: Line item to add to cart (required)
          :return: ShoppingCart
                   If the method is called asynchronously,
                   returns the request thread.