code: func (h *Handle) IsSet(ordinal uint64) bool {
  	if err := h.validateOrdinal(ordinal); err != nil {
  		return false
  	}
  	h.Lock()
  	_, _, err := checkIfAvailable(h.head, ordinal)
  	h.Unlock()
  	return err != nil
  }
docs: // IsSet atomically checks if the ordinal bit is set. In case ordinal
  // is outside of the bit sequence limits, false is returned.