input: Write a python function to calculate the total price of items in a vending machine.
  assert vending_machine.calculate_total_price([coke, chips]) == 1.75
  assert vending_machine.calculate_total_price([]) == 0
  assert vending_machine.calculate_total_price([Item('Water', 2.00, 3)]) == 6.00
output: class Item:
      def __init__(self, name, price, quantity=1):
          self.name = name
          self.price = price
          self.quantity = quantity
  
  class VendingMachine:
      def calculate_total_price(self, items):
          total_price = sum(item.price * item.quantity for item in items)
          return total_price
  
  # Example items
  coke = Item('Coke', 1.00)
  chips = Item('Chips', 0.75)
  
  # Create a vending machine instance
  vending_machine = VendingMachine()