input: Write a function to calculate the total cost of a shopping cart considering the item prices, quantity, shipping cost, and any applicable taxes. If the shopping cart is empty, return 0.0.
  assert shopping_cart_cost([{"name": "widget", "price": 10, "quantity": 5 }, {"name": "thingy", "price": 7, "quantity": 3 }, {"name": "doodad", "price": 5, "quantity": 2 }], 7.50, 0.095) == 122.07
  assert shopping_cart_cost([], 7.50, 0.095) == 0.0
  assert shopping_cart_cost([{"name": "shirt", "price": 20, "quantity": 2 }], 10.00, 0.10) == 54.00
output: def shopping_cart_cost(cart, shipping_cost, tax_rate):
      if not cart:
          return 0.0
      subtotal = sum(item['price'] * item['quantity'] for item in cart)
      total_cost = subtotal + shipping_cost
      total_cost += total_cost * tax_rate
      return round(total_cost, 2)