input: Write a function to create a Python class that takes a given number and calculates the sum of its digits. The class should have a method called `calculate_sum_of_digits` which returns the sum of the digits.
  assert type(SumOfDigits(6342)).__name__ == 'SumOfDigits'
  assert SumOfDigits(6342).calculate_sum_of_digits() == 15
  assert SumOfDigits(12345).calculate_sum_of_digits() == 15
output: class SumOfDigits:
      def __init__(self, number):
          self.number = number
      
      def calculate_sum_of_digits(self):
          return sum(int(digit) for digit in str(self.number))