default @Nullable PsiElement getCustomDocumentationElement(final @NotNull Editor editor,
                                                   final @NotNull PsiFile file,
                                                   @Nullable PsiElement contextElement,
                                                   int targetOffset) {
    //noinspection deprecation
    return (this instanceof DocumentationProviderEx)
           ? ((DocumentationProviderEx)this).getCustomDocumentationElement(editor, file, contextElement)
           : null;
  }
default @Nullable PsiElement getCustomDocumentationElement(final @NotNull Editor editor,
                                                   final @NotNull PsiFile file,
                                                   @Nullable PsiElement contextElement,
                                                   int targetOffset)