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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 add_callback(self, callback: callable):
 """ Add a callback on change :param callback: callable function :return: None """

        def internal_callback(*args):
            try:
                callback()
            except TypeError:
                callback(self.get())

        self._var.trace('w', internal_callback)