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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 notify(self, instance, old, new):
 """ Call all callback functions with the current value Each callback will either be called using callback(new) or callback(old, new) depending on whether ``echo_old`` was set to `True` when calling :func:`~echo.add_callback` Parameters instance The instance to consider old The old value of the property new The new value of the property """

        if self._disabled.get(instance, False):
            return
        for cback in self._callbacks.get(instance, []):
            cback(new)
        for cback in self._2arg_callbacks.get(instance, []):
            cback(old, new)