code: def get_upgrades(self, remove_applied=True):
          
          if self.upgrades is None:
              plugins = self._load_upgrades(remove_applied=remove_applied)
  
              # List of un-applied upgrades in topological order
              self.upgrades = self.order_upgrades(plugins, self.history)
          return self.upgrades
docs: Get upgrades (ordered according to their dependencies).
  
          :param remove_applied: Set to false to return all upgrades, otherwise
              already applied upgrades are removed from their graph (incl. all
              their dependencies.