input: Write a function to implement a class named Calculator which has two methods: one for adding two numbers and another for adding three numbers. The class should have an initializer that does nothing. If the given inputs are integers or floats, the functions should return the sum of the inputs.
  assert Calculator().add_two_numbers(1, 2)==3
  assert Calculator().add(1, 2, 3)==6
  assert Calculator().add_two_numbers(-1, -2)==-3
  assert Calculator().add(0, 0, 0)==0
  assert Calculator().add_two_numbers(1.5, 2.5)==4.0
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