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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 get_percentage_volume_change(self):
 """ Returns the percentage volume change. Returns: Volume change in percentage, e.g., 0.055 implies a 5.5% increase. """

        initial_vol = self.initial.lattice.volume
        final_vol = self.final.lattice.volume
        return final_vol / initial_vol - 1