input: Write a python function to sum odd digits of a number.
  assert sum_odd_digits(2243) == 7
  assert sum_odd_digits(13579) == 25
  assert sum_odd_digits(2468) == 0
output: def sum_odd_digits(n):
      return sum(int(digit) for digit in str(n) if int(digit) % 2 != 0)