@Nullable
  public PsiElement getCheckBox() {
    final PsiElement markerElement = getMarkerElement();
    if (markerElement == null) {
      return null;
    }
    final PsiElement candidate = markerElement.getNextSibling();
    if (candidate != null && candidate.getNode().getElementType() == MarkdownTokenTypes.CHECK_BOX) {
      return candidate;
    }
    else {
      return null;
    }
  }
@Nullable
  public PsiElement getCheckBox()