input: Write a function to calculate the sum of the digits in a given number. If the number is negative, ignore the negative sign and calculate the sum of the digits. If the number is zero, return zero.
  
  def sum_digits(num):
      total = 0
      num = abs(num)
      while num > 0:
          digit = num % 10
          total += digit
          num = num // 10
      return total
  
  assert sum_digits(123)==6
  assert sum_digits(456)==15
  assert sum_digits(-789)==24
  assert sum_digits(0)==0
output: def sum_digits(num):
      total = 0
      num = abs(num)
      while num > 0:
          digit = num % 10
          total += digit
          num = num // 10
      return total