input: Write a python function to create a Stock class that can add and get prices.
  assert AAPL.get_prices() == [191.43, 193.57, 190.08]
  assert isinstance(AAPL, Stock)
  AAPL.add_price(195.67)
  assert AAPL.get_prices() == [191.43, 193.57, 190.08, 195.67]
output: class Stock:
      def __init__(self, symbol):
          self.symbol = symbol
          self.prices = []
          
      def add_price(self, price):
          self.prices.append(price)
          
      def get_prices(self):
          return self.prices
  
  AAPL = Stock("AAPL")
  AAPL.add_price(191.43)
  AAPL.add_price(193.57)
  AAPL.add_price(190.08)