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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def encode(self, formatter=None):
 """Return a representation of the cart as a JSON-response. Parameters formatter : func, optional A function that accepts the cart representation and returns its formatted version. Returns ------- django.http.JsonResponse Examples -------- Assume that items with primary keys "1" and "4" are already in the cart. b'{ "items": { '1': {"price": 100, "quantity": 10, "total": 1000}, '4': {"price": 50, "quantity": 20, "total": 1000}, }, "itemCount": 2, "totalPrice": "2,000", }' """

        items = {}
        # The prices are converted to strings, because they may have a
        # type that can't be serialized to JSON (e.g. Decimal).
        for item in self.items.values():
            pk = str(item.obj.pk)
            items[pk] = {
                'price': str(item.price),
                'quantity': item.quantity,
                'total': item.total,
            }
        cart_repr = {
            'items': items,
            'itemCount': self.item_count,
            'totalPrice': str(self.total_price),
        }
        if formatter:
            cart_repr = formatter(cart_repr)
        return JsonResponse(cart_repr)