public static PsiElement getOnlyChild(PsiElement element, @NotNull NodeFilter filter) {
    FilteringNodeIterator it = new FilteringNodeIterator(SiblingNodeIterator.create(element.getFirstChild()), filter);
    PsiElement child = it.current();
    if (child != null) {
      it.advance();
      if (!it.hasNext()) {
        return child;
      }
    }
    return element;
  }
public static PsiElement getOnlyChild(PsiElement element, @NotNull NodeFilter filter)