input: Write a python function to predict stock prices using the moving average.
  assert stock_price_prediction([10, 20, 30, 40, 50, 60, 70, 80, 90, 100])==55.0
  assert stock_price_prediction([5, 15, 25, 35, 45])==25.0
  assert stock_price_prediction([100, 200, 300, 400])==250.0
output: def stock_price_prediction(prices):
      return sum(prices) / len(prices)