input: Write a function to predict the next day's forecast temperature using the exponential smoothing algorithm given the past three day's forecast temperatures. The function should return the predicted temperature.
  assert predict_temperature([21, 22, 20]) == 20.75
  assert predict_temperature([19, 21, 21]) == 20.625
  assert predict_temperature([22, 23, 24]) == 23.75
  assert predict_temperature([18, 17, 19]) == 18.25
  assert predict_temperature([20, 20, 20]) == 20
output: def predict_temperature(temps):
      alpha = 0.5
      return alpha * temps[2] + (1 - alpha) * (alpha * temps[1] + (1 - alpha) * temps[0])