input: Write a function to construct a Python class that takes a given number and calculates the sum of the digits. The class should have an initializer method that accepts the number and a method to calculate the sum of its digits.
  assert SumOfDigits(6342).calculate_sum_of_digits()==15
  assert SumOfDigits(12345).calculate_sum_of_digits()==15
  assert SumOfDigits(0).calculate_sum_of_digits()==0
  assert SumOfDigits(987654321).calculate_sum_of_digits()==45
  assert SumOfDigits(11223344).calculate_sum_of_digits()==20
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))