def cancel(self):
            """Cancels the instances current subscriptions. Setting self.subscrptn1
            to None removes the reference to the subscription object, causing it's 
            finalizer (__del__) method to be called."""
            self.subscrptn1 = None
            self.subscrptn2 = None
            self.subscrptn3 = None
Cancels the instances current subscriptions. Setting self.subscrptn1
            to None removes the reference to the subscription object, causing it's 
            finalizer (__del__) method to be called.
recipes/Python/578038_Observer_pattern_implemented_Descriptor/recipe-578038.py