offset(offset) {
    this.startTime += offset;
    this.endTime += offset;
    this.trueEndTime += offset;

    for (const partial of this.partialReferences) {
      partial.startTime += offset;
      partial.endTime += offset;
      partial.trueEndTime += offset;
    }
  }
Offset the segment reference by a fixed amount.

@param {number} offset The amount to add to the segment's start and end
  times.
@export