input: 
  def predict_annual_income(age: int, education_level: int) -> float:
      """
      Predicts the annual income based on the provided age and education level using a pre-trained neural network model.
      The education level should be provided as an integer, where 0 represents high school, 1 represents college, 
      2 represents undergraduate, and 3 represents postgraduate.
      
      >>> predict_annual_income(50, 3)
      80000.0
      """
  
output:     if education_level < 0 or education_level > 3:
          raise ValueError("Invalid education level. It should be between 0 and 3.")
      
      # Simple linear model for demonstration purposes
      income = 20000 + 1000 * age + 10000 * education_level
      
      return float(income)