code: func (h *Handle) SetAnyInRange(start, end uint64, serial bool) (uint64, error) {
  	if end < start || end >= h.bits {
  		return invalidPos, fmt.Errorf("invalid bit range [%d, %d]", start, end)
  	}
  	if h.Unselected() == 0 {
  		return invalidPos, ErrNoBitAvailable
  	}
  	return h.set(0, start, end, true, false, serial)
  }
docs: // SetAnyInRange atomically sets the first unset bit in the specified range in the sequence and returns the corresponding ordinal