input: Write a function to implement a Python class named `Calculator` which has two methods: `add_two_numbers` and `add`. The `add_two_numbers` method should take two arguments and return their sum. The `add` method should take three arguments and return their sum.
  
  
  class Calculator:
      def __init__(self):
          pass
      
      def add_two_numbers(self, a, b):
          return a + b
  
      def add(self, a, b, c):
          return a + b + c
  
  calculator = Calculator()
  result = calculator.add_two_numbers(1, 2)
  assert result == 3
  result = calculator.add(1, 2, 3)
  assert result == 6
  
output: class Calculator:
      def __init__(self):
          pass
      
      def add_two_numbers(self, a, b):
          return a + b
  
      def add(self, a, b, c):
          return a + b + c