code: def retrieve(self, order_id, id) :
          
  
          _, _, line_item = self.http_client.get("/orders/{order_id}/line_items/{id}".format(order_id=order_id, id=id))
          return line_item
docs: Retrieve a single line item
  
          Returns a single line item of an order, according to the unique line item ID provided
  
          :calls: ``get /orders/{order_id}/line_items/{id}``
          :param int order_id: Unique identifier of a Order.
          :param int id: Unique identifier of a LineItem.
          :return: Dictionary that support attriubte-style access and represent LineItem resource.
          :rtype: dict