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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 prepend(self, tr):
 """ Add a new transform to the beginning of this chain. Parameters tr : instance of Transform The transform to use. """

        self.transforms.insert(0, tr)
        tr.changed.connect(self._subtr_changed)
        self._rebuild_shaders()
        self.update()