input: Write a function to calculate the sum of the digits in a given number. The function should take an integer as input and return the sum of its digits. If the given number is negative, it should be treated as positive for the sum calculation.
  assert sum_digits(123)==6
  assert sum_digits(456789)==39
  assert sum_digits(0)==0
  assert sum_digits(-1234)==10
output: def sum_digits(n):
      n = abs(n)
      return sum(int(digit) for digit in str(n))