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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 callback(self, callback):
 """ Set callback for callback queries :Example: """

        if callable(callback):
            self._default_callback = callback
            return callback
        elif isinstance(callback, str):

            def decorator(fn):
                self.add_callback(callback, fn)
                return fn

            return decorator
        else:
            raise TypeError("str expected {} given".format(type(callback)))