input: Write a function in Python that defines a class Calculator with two methods to add either two or three numbers respectively. The function should pass the following asserts for each method:
  assert Calculator().add_two_numbers(1, 2) == 3
  assert Calculator().add(1, 2, 3) == 6
  if the function is correctly implemented, return True; otherwise, return False.
output: class Calculator:
      def add_two_numbers(self, a, b):
          return a + b
      
      def add(self, a, b, c):
          return a + b + c