docs: def _priority_range(policy=None):
      """Determine the priority range (min,max) for the given scheduler policy.
  
      If no policy is specified, the current default policy is used.
      """
      if policy is None:
          policy = libc.sched_getscheduler(0)
          if policy < 0:
              raise OSError(get_errno(),"sched_getscheduler")
      max = libc.sched_get_priority_max(policy)
      if max < 0:
          raise OSError(get_errno(),"sched_get_priority_max")
      min = libc.sched_get_priority_min(policy)
      if min < 0:
          raise OSError(get_errno(),"sched_get_priority_min")
      return (min,max)