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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 _update(self, *_):
 """Set target value to source value"""

        if getattr(self, '_unlinked', False):
            return
        if getattr(self, '_updating', False):
            return
        self._updating = True
        try:
            setattr(self.target[0], self.target[1], self.transform(
                getattr(self.source[0], self.source[1])
            ))
        finally:
            self._updating = False