code: def change_item(self, item_id, operation):
          
  
          product = Products().get_one(item_id)
          if product:
              if operation == 'add':
                  self.items.append(product)
              elif operation == 'remove':
                  cart_p = [x for x in self.items if x['id'] == product['id']]
                  self.items.remove(cart_p[0])
              self.update()
              return True
          else:
              return False
docs: Remove items in cart