docs: def _add_stage(self, name):
          """ Add stage methods at runtime.
  
          Stage methods all follow the same pattern.
  
          :param name: Stage name.
          """
          def stage_func(self, *args, **kwargs):
              """ Stage function.
  
              :param args: Positional arguments.
              :param kwargs: Keyword arguments.
              :return: Pipeline (for method chaining).
              """
              self._pipe.append(Stage(name, args, kwargs))
              return self
  
          setattr(Pipeline, name, stage_func)