input: Write a class that takes a number and calculates the sum of its digits. If the number is negative, ignore the negative sign while calculating the sum.
  
  class SumOfDigits:
      
      def __init__(self, num):
          self.num = abs(num)
      
      def calculate_sum_of_digits(self):
          total = 0
          for ch in str(self.num):
              total += int(ch)
          return total
  
  assert SumOfDigits(6342).calculate_sum_of_digits() == 15
  assert SumOfDigits(-6342).calculate_sum_of_digits() == 15
  assert SumOfDigits(123).calculate_sum_of_digits() == 6
  assert SumOfDigits(-123).calculate_sum_of_digits() == 6
  assert SumOfDigits(0).calculate_sum_of_digits() == 0
output: 
  class SumOfDigits:
      
      def __init__(self, num):
          self.num = abs(num)
      
      def calculate_sum_of_digits(self):
          total = 0
          for ch in str(self.num):
              total += int(ch)
          return total
  