input: from typing import List, Dict
  
  def calculate_total_cost(items: List[Dict[str, float]], shipping_cost: float, tax_rate: float) -> float:
      """Calculate the total cost of a shopping cart given item prices, quantities, shipping cost, and tax rate.
      
      >>> items = [
      ...     {"name": "widget", "price": 10, "quantity": 5 },
      ...     {"name": "thingy", "price": 7, "quantity": 3 },
      ...     {"name": "doodad", "price": 5, "quantity": 2 },
      ... ]
      >>> shipping_cost = 7.50
      >>> tax_rate = 0.095
      >>> calculate_total_cost(items, shipping_cost, tax_rate)
      121.675
      """
      total_cost = 0
      for item in items:
          total_cost += item['price'] * item['quantity']
      
      total_cost += total_cost * tax_rate
      total_cost += shipping_cost
      
      return round(total_cost, 3)
output:     total_cost = 0
      for item in items:
          total_cost += item['price'] * item['quantity']
      
      total_cost += total_cost * tax_rate
      total_cost += shipping_cost
      
      return round(total_cost, 3)