static newDisconnected(id, allPrevSegments) {
    return new CodePathSegment(id, [], allPrevSegments.some(isReachable));
  }
Creates a segment that follows given segments.
This factory method does not connect with `allPrevSegments`.
But this inherits `reachable` flag.
@param {string} id An identifier.
@param {CodePathSegment[]} allPrevSegments An array of the previous segments.
@returns {CodePathSegment} The created segment.