请问beamer目录的section和subsection的标记如何改成类似于item的circle样式？

如果你是要例子，下面这个例子看看，这些细节定制，需要改template的：

\documentclass[t,compress,11pt,xcolor=dvipsnames]{beamer}
\definecolor{LHCblue}{RGB}{4, 114, 255}
\usecolortheme[named=LHCblue]{structure}
\usepackage[bars]{beamerthemetree} %Beamer theme v 2.2
\usefonttheme[onlymath]{serif}
\usepackage{kerkis}
\setbeamercovered{higly dynamic}
\usetheme{Ilmenau} % Beamer theme v 3.0
\useoutertheme[subsection=true]{smoothbars}%Beamer Outer Theme-circles on top
\usefonttheme{serif}
\useinnertheme{circles} %rectangle bullet points instead of circle ones
\usepackage{beamerthemebars}

\setbeamerfont{section in toc}{size=\tiny}
\setbeamerfont{subsection in toc}{size=\tiny}

\title[Short Title]{Full Title}
\author{Author}
\institute{Institute}

\begin{document}

\begin{frame}
\titlepage
\end{frame}

\begin{frame}
\frametitle{Contents}
\tableofcontents
\end{frame}

\section{first section}
\begin{frame}
Intro to section
\end{frame}

\subsection{first subsection}
\begin{frame}
Theory
\end{frame}

\subsection{second subsection}
\begin{frame}
Experiment
\end{frame}

\subsection{third subsection}
\begin{frame}
Results
\end{frame}

\section{Back up slides}

\begin{frame}
1st Back up slide
\end{frame}

\begin{frame}
2nd Back up slide
\end{frame}

\begin{frame}
3rd Back up slide
\end{frame}

\end{document}