input: Write a function to calculate the sum of the digits in a given number. If the given number is negative, return the sum of the digits in the absolute value of the number. If the number is zero, return zero.
  assert sum_digits(123) == 6
  assert sum_digits(4567) == 22
  assert sum_digits(-123) == 6
  assert sum_digits(0) == 0
output: def sum_digits(num):
      num = abs(num)
      return sum(int(digit) for digit in str(num))