input: Write a function that defines a class with two methods for adding two numbers and testing the methods using assert statements. The first method should take two arguments and return their sum, while the second method should take three arguments and return their sum. The class should be named Calculator and should include an empty constructor.
  
  
  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
  
  
  assert Calculator().add_two_numbers(1, 2) == 3
  assert Calculator().add(1, 2, 3) == 6
  assert Calculator().add_two_numbers(-1, 1) == 0
  assert Calculator().add(0, -1, 1) == 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