docs: def _description(self):
          """A concise html explanation of this Action."""
  
          inst = self.timemachine.presently
  
          if self.action_type == "dl":
              return "Deleted %s" % inst.content_type.name
          elif self.action_type == "cr":
              return "Created %s" % inst._object_type_html()
          else:
              return "Modified %s" % inst._object_type_html()