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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_upgrade_prices(self, instance_id, include_downgrade_options=True):
 """Following Method gets all the price ids related to upgrading a VS. :param int instance_id: Instance id of the VS to be upgraded :returns: list """

        mask = [
            'id',
            'locationGroupId',
            'categories[name,id,categoryCode]',
            'item[description,capacity,units]'
        ]
        mask = "mask[%s]" % ','.join(mask)
        return self.guest.getUpgradeItemPrices(include_downgrade_options, id=instance_id, mask=mask)