input: Write a function to complete the request described in the instruction. The function should define a Python class named Calculator with two methods: add_two_numbers and add. The add_two_numbers method should accept two numbers as arguments and return their sum. The add method should accept three numbers as arguments and return their sum.
  assert Calculator().add_two_numbers(1, 2) == 3
  assert Calculator().add(1, 2, 3) == 6
  assert Calculator().add_two_numbers(5, 10) == 15
  assert Calculator().add(-1, -1, -1) == -3
  assert Calculator().add_two_numbers(0, 0) == 0
output: class Calculator:
      def add_two_numbers(self, a, b):
          return a + b
      
      def add(self, a, b, c):
          return a + b + c