constructor(segmentIndex, index, partialSegmentIndex, reverse) {
    /** @private {shaka.media.SegmentIndex} */
    this.segmentIndex_ = segmentIndex;

    /** @private {number} */
    this.currentPosition_ = index;

    /** @private {number} */
    this.currentPartialPosition_ = partialSegmentIndex;

    /** @private {boolean} */
    this.reverse = reverse;
  }
@param {shaka.media.SegmentIndex} segmentIndex
@param {number} index
@param {number} partialSegmentIndex
@param {boolean} reverse