'Cart' object has no attribute 'add'

from django.shortcuts import render, redirect, get_object_or_404
from cart.cart import add
from django.views.decorators.http import require_POST
from shop.models import Product
from .cart import Cart
from .forms import CartAddProductForm
 
 
@require_POST
def cart_add(request, product_id):
    cart = Cart(request)
    product = get_object_or_404(Product, id=product_id)
    form = CartAddProductForm(request.POST)
    if form.is_valid():
        cd = form.cleaned_data
        [B]cart.add(product=product,
                 quantity=cd['quantity'],
                 update_quantity=cd['update'])[/B] - [SIZE="3"]Ругается вот на эту строчку, хотя я по уроку делаю , и этот код просто скопирован с сайта. И у них там все прекрасно работает.[/SIZE]
    return redirect('cart:cart_detail')
 
def cart_remove(request, product_id):
    cart = Cart(request)
    product = get_object_or_404(Product, id=product_id)
    cart.remove(product)
    return redirect('cart:cart_detail')
 
def cart_detail(request):
    cart = Cart(request)
    return render(request, 'cart/detail.html', {'cart': cart})

from django.conf.urls import url
from . import views
 
 
urlpatterns = [
    url(r'^$', views.cart_detail, name='cart_detail'),
    url(r'^add/(?P<product_id>\d+)/$', views.cart_add, name='cart_add'),
    url(r'^remove/(?P<product_id>\d+)/$', views.cart_remove, name='cart_remove'),
]