:return:
        a pair producer that ensures the seeder and delegator share the same event space.

def pave_event_space(fn=pair):
    """
    :return:
        a pair producer that ensures the seeder and delegator share the same event space.
    """
    global _event_space
    event_space = next(_event_space)

    @_ensure_seeders_list
    def p(seeders, delegator_factory, *args, **kwargs):
        return fn(seeders + [per_event_source_id(event_space)],
                  delegator_factory, *args, event_space=event_space, **kwargs)
    return p