docs: 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