input: Write a python function to test the methods of MyClass.
  assert test_myclass_methods() == (5, 1, -1)
  assert test_myclass_methods() == (10, 2, -2)
  assert test_myclass_methods() == (15, 3, -3)
output: def test_myclass_methods():
      class MyClass:
          def __init__(self, value):
              self.value = value
  
          def add(self, num):
              self.value += num
              return self.value
  
          def subtract(self, num):
              self.value -= num
              return self.value
  
          def multiply(self, num):
              self.value *= num
              return self.value
  
      instance1 = MyClass(0)
      instance2 = MyClass(1)
      instance3 = MyClass(2)
  
      result1 = instance1.add(5)
      result1 = instance1.subtract(4)
      result1 = instance1.multiply(-1)
  
      result2 = instance2.add(9)
      result2 = instance2.subtract(8)
      result2 = instance2.multiply(-1)
  
      result3 = instance3.add(13)
      result3 = instance3.subtract(12)
      result3 = instance3.multiply(-1)
  
      return result1, result2, result3