Я получаю ошибку [<class 'decimal.ConversionSyntax'>] в моей корзине, как это исправить?

При добавлении товара в корзину возникает ошибка InvalidOperation at /cart/ [<class 'decimal.ConversionSyntax'>].

Мой код:

cart..py ...............................

from decimal import Decimal
from django.conf import settings
from TeaYardApp.models import Products


class Cart(object):

    def __init__(self, request):
        self.session = request.session
        cart = self.session.get(settings.CART_SESSION_ID)
        if not cart:
            cart = self.session[settings.CART_SESSION_ID] = {}
        self.cart = cart

    def __iter__(self):
        product_ids = self.cart.keys()
        # получаем товары и добавляем их в корзину
        product = Products.objects.filter(id__in=product_ids)

        cart = self.cart.copy()
        for product in product:
            cart[str(product.id)]['product'] = product

        for item in cart.values():
            item['price'] = Decimal(item['price'])
            item['total_price'] = item['price'] * item['quantity']
            yield item

    def __len__(self):
        return sum(item['quantity'] for item in self.cart.values())

    def add(self, product, quantity=1, update_quantity=False):
        product_id = str(product.id)
        if product_id not in self.cart:
            self.cart[product_id] = {'quantity': 0,
                                     'price': str(product.price)}
        if update_quantity:
            self.cart[product_id]['quantity'] = quantity
        else:
            self.cart[product_id]['quantity'] += quantity
        self.save()

    def save(self):
        self.session.modified = True

    def remove(self, product):
        product_id = str(product.id)
        if product_id in self.cart:
            del self.cart[product_id]
            self.save()

    def get_total_price(self):
        return sum(Decimal(item['price']) * item['quantity'] for item in self.cart.values())

    def clear(self):
        del self.session[settings.CART_SESSION_ID]
        self.save()

Форма для добавления товаров в корзину, forms.py ..................................

from django import forms

PRODUCT_QUANTITY_CHOICES = [(i, str(i)) for i in range(25, 200+1, 25)]


class CartAddProductForm(forms.Form):
    quantity = forms.TypedChoiceField(
        choices=PRODUCT_QUANTITY_CHOICES,
        coerce=int)
    update = forms.BooleanField(required=False,
                                initial=False,
                                widget=forms.HiddenInput)

Я не знаю, как исправить эту ошибку, помогите, пожалуйста. ....................................

Traceback:

Traceback (most recent call last):
  File "C:\my_projects\TeaYard\venv\lib\site-packages\django\core\handlers\exception.py"
, line 55, in inner
    response = get_response(request)
  File "C:\my_projects\TeaYard\venv\lib\site-packages\django\core\handlers\base.py", lin
e 197, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "C:\my_projects\TeaYard\App\cart\views.py", line 30, in cart_detail
    for item in cart:
  File "C:\my_projects\TeaYard\App\cart\cart.py", line 28, in __iter__
    item['price'] = Decimal(item['price'])
decimal.InvalidOperation: [<class 'decimal.ConversionSyntax'>]

def get_total_price(self):
    price = item['price'] if item['price'] else 0
    return sum(Decimal(price) * item['quantity'] for item in self.cart.values())

item['price'] = Decimal(item['price'])

# convert to string first (to be able call isnumeric method)
price = str(item['price'])
# check if price string is numeric
if price.isnumeric()
  price = Decimal(price)
else:
  # handle bad value (raise error or whatever depending on your logic)
  raise ValueError('price must be numeric value')