code: def pair(seeders, delegator_factory, *args, **kwargs):
      
      return (chain(*seeders) if len(seeders) > 1 else seeders[0],
              delegator_factory(*args, **kwargs))
docs: The basic pair producer.
  
      :return:
          a (seeder, delegator_factory(\*args, \*\*kwargs)) tuple.
  
      :param seeders:
          If it is a seeder function or a list of one seeder function, it is returned
          as the final seeder. If it is a list of more than one seeder function, they
          are chained together before returned as the final seeder.