input: Write a function to implement a Calculator class in Python that includes two methods to add two numbers and another method to add three numbers. The first method should take two arguments and return their sum. The second method should take three arguments and return their sum. If the class is instantiated correctly and the methods are called with appropriate parameters, they should return the sum of the provided numbers.
  
  class Calculator:
   def __init__(self):
     pass
      
   def add_two_numbers(self, a, b):
     return a + b
  
   def add_three_numbers(self, a, b, c):
     return a + b + c
  
  assert Calculator().add_two_numbers(1, 2) == 3
  assert Calculator().add_two_numbers(10, 5) == 15
  assert Calculator().add_three_numbers(1, 2, 3) == 6
  assert Calculator().add_three_numbers(5, 10, 15) == 30
  assert Calculator().add_two_numbers(-1, -1) == -2
  assert Calculator().add_three_numbers(0, 0, 0) == 0
output: class Calculator:
   def __init__(self):
     pass
      
   def add_two_numbers(self, a, b):
     return a + b
  
   def add_three_numbers(self, a, b, c):
     return a + b + c