input: Write a function to calculate the total cost of a shopping cart considering the item prices, quantity, shipping cost, and any applicable taxes. Return the total cost as a float. If the items list is empty, return 0.
  assert calculate_total_cost(
   [ 
    {"name": "widget", "price": 10, "quantity": 5 },
    {"name": "thingy", "price": 7, "quantity": 3 },
    {"name": "doodad", "price": 5, "quantity": 2 },
   ], 7.50, 0.095
  )==125.33875
  assert calculate_total_cost([], 7.50, 0.095)==0
  assert calculate_total_cost(
   [ 
    {"name": "fancyhat", "price": 25, "quantity": 1 },
   ], 5.00, 0.10
  )==33.0
output: def calculate_total_cost(items, shipping_cost, tax_rate):
      if not items:
          return 0
      subtotal = sum(item["price"] * item["quantity"] for item in items)
      total_cost = subtotal + shipping_cost
      total_cost += total_cost * tax_rate
      return total_cost