(callback)
Add a listener. The arguments to the callback are determined by whomever calls notify()
Add a listener. The arguments to the callback are determined by whomever calls notify()
Add a listener . The arguments to the callback are determined by whomever calls notify ()
def add(callback):
        """
        Add a listener. The arguments to the callback are determined by whomever calls notify()
        """
def add ( callback ) :