new_contents: def sum_of_digits(n: int) -> int:
      """
      Find the sum of digits of a number.
  
      >>> sum_of_digits(12345)
      15
      >>> sum_of_digits(123)
      6
      """
      res = 0
      while n > 0:
          res += n % 10
          n = n // 10
      return res
  
  
  if __name__ == "__main__":
      print(sum_of_digits(12345))  # ===> 15
  
subject: create sum_of_digits.py (#2065)