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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 applied():
 """Command for showing all upgrades already applied."""

    upgrader = InvenioUpgrader()
    logger = upgrader.get_logger()

    try:
        upgrades = upgrader.get_history()

        if not upgrades:
            logger.info("No upgrades have been applied.")
            return

        logger.info("Following upgrade(s) have been applied:")

        for u_id, applied in upgrades:
            logger.info(" * %s (%s)" % (u_id, applied))
    except RuntimeError as e:
        for msg in e.args:
            logger.error(unicode(msg))
        raise