docs: def listcall(self, *arg, **kw):
          """Call each plugin sequentially.
  
          Return the first result that is not None.
          """
          final_result = None
          for _, meth in self.plugins:
              result = meth(*arg, **kw)
              if final_result is None and result is not None:
                  final_result = result
          return final_result