_createPagesHelper() {
    const iterator = this.form[$toPages]();
    return new Promise((resolve, reject) => {
      const nextIteration = () => {
        try {
          const value = iterator.next();
          if (value.done) {
            resolve(value.value);
          } else {
            setTimeout(nextIteration, 0);
          }
        } catch (e) {
          reject(e);
        }
      };
      setTimeout(nextIteration, 0);
    });
  }
In order to avoid to block the event loop, the conversion
into pages is made asynchronously.