code: def ensure_pool(func):
      
      def func_wrapper(*args, **kwargs):
          if len(args) == 0 or not isinstance(args[0], Stepper):
              raise Exception('@ensure_pool can only be used on Stepper methods.')
          if args[0]._pool is None:
              with args[0]:
                  return func(*args, **kwargs)
          else:
              return func(*args, **kwargs)
      return func_wrapper
docs: Decorator that ensures a pool is available for a stepper.