private static Computable<Collection<StructureViewTreeElement>> createChildrenComputable(final Collection<Section> children) {
    return () -> {
      final Collection<StructureViewTreeElement> result = new ArrayList<>();
      for (Section section : children) {
        result.add(createHtml5SectionTreeElement(section));
      }
      return result;
    };
  }
private static Computable<Collection<StructureViewTreeElement>> createChildrenComputable(final Collection<Section> children)