input: 
  def evaluate_expression(expr: str) -> float:
      """ Evaluate a given numerical expression and return the result.
      >>> evaluate_expression("2 + 3 * 4")
      14.0
      >>> evaluate_expression("(2 + 3) * 4")
      20.0
      >>> evaluate_expression("10 / 2 - 3")
      2.0
      """
      return eval(expr)
  
output:     try:
          result = eval(expr)
          return float(result)
      except Exception as e:
          raise ValueError(f"Invalid expression: {expr}")