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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def orify(event, changed_callback):
    '''
    Override ``set`` and ``clear`` methods on event to call specified callback
    function after performing default behaviour.

    Parameters
    ----------

    '''
    event.changed = changed_callback
    if not hasattr(event, '_set'):
        # `set`/`clear` methods have not been overridden on event yet.
        # Override methods to call `changed_callback` after performing default
        # action.
        event._set = event.set
        event._clear = event.clear
        event.set = lambda: or_set(event)
        event.clear = lambda: or_clear(event)