get modifiedIds() {
    if (this.#modifiedIds) {
      return this.#modifiedIds;
    }
    const ids = [];
    for (const value of this.#storage.values()) {
      if (
        !(value instanceof AnnotationEditor) ||
        !value.annotationElementId ||
        !value.serialize()
      ) {
        continue;
      }
      ids.push(value.annotationElementId);
    }
    return (this.#modifiedIds = {
      ids: new Set(ids),
      hash: ids.join(","),
    });
  }
@returns {{ids: Set<string>, hash: string}}