input: Write a function to construct a Python class that takes a given number and calculates the sum of the digits. The class should include a method that performs the calculation.
  assert SumOfDigits(6342).calculate_sum_of_digits() == 15
  assert SumOfDigits(1234).calculate_sum_of_digits() == 10
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))