input: 
  class SumOfDigits:
      
      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
  
  digit_sum = SumOfDigits(6342)
  result = digit_sum.calculate_sum_of_digits()
  print(result)
  
  
  **Expected Output:**
  
  15
  
output:     
  class SumOfDigits:
      
      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
  
  digit_sum = SumOfDigits(6342)
  result = digit_sum.calculate_sum_of_digits()
  print(result)
  