input: Write a python function to dispense an item from a vending machine based on input amount and calculate the change.
  assert vm.dispenseItem(2.75) == 'Dispensing: Chips\nChange remaining: 1.25'
  assert vm.dispenseItem(1.25) == 'Dispensing: Soda\nChange remaining: 0.0'
  assert vm.dispenseItem(2.25) == 'Dispensing: Snickers\nChange remaining: 0.0'
output: class VendingMachine:
      def __init__(self):
          self.items = {
              'Chips': 1.50,
              'Soda': 1.25,
              'Snickers': 2.25
          }
  
      def dispenseItem(self, amount):
          for item, price in sorted(self.items.items(), key=lambda x: -x[1]):
              if amount >= price:
                  change = round(amount - price, 2)
                  return f'Dispensing: {item}\nChange remaining: {change}'
  
  vm = VendingMachine()