add(segments) {
    assert(
      segments.length >= this.count,
      `${segments.length} >= ${this.count}`,
    );

    this.segmentsList.push(mergeExtraSegments(this, segments));
  }
Adds segments into this context.
The added segments become the head.
@param {CodePathSegment[]} segments Segments to add.
@returns {void}