input: 
  from typing import List
  
  def predict_temperature(temperature_list: List[float]) -> float:
      """This code uses the exponential smoothing algorithm to predict the next day's forecasted temperature given the past three day's forecasted temperatures.
      >>> predict_temperature([21, 22, 20])
      21.0
      """
      alpha = 0.5 #Confidence value
      predicted_temperature = temperature_list[-1] # Initializing prediction
      for temperature in temperature_list[:-1]:
          predicted_temperature = alpha*temperature + (1-alpha)*predicted_temperature
      return predicted_temperature
  
output:     alpha = 0.5 #Confidence value
      predicted_temperature = temperature_list[-1] # Initializing prediction
      for temperature in temperature_list[:-1]:
          predicted_temperature = alpha*temperature + (1-alpha)*predicted_temperature
      return predicted_temperature