input: 
  class SumOfDigits:
      """
      A class that takes a given number and calculates the sum of its digits.
      
      >>> digit_sum = SumOfDigits(6342)
      >>> result = digit_sum.calculate_sum_of_digits()
      >>> print(result)
      15
      """
      
      def __init__(self, num):
          self.num = num
      
      def calculate_sum_of_digits(self):
          total = 0
          for ch in str(self.num):
              total += int(ch)
          return total
  
output:     def calculate_sum_of_digits(self):
          total = 0
          for ch in str(self.num):
              total += int(ch)
          return total