\test 定义中的参数编号非法

Question

我的问题是使用 beamer 类将以下内容放到演示文稿的框架上。我收到以下错误消息：

\test 定义中的参数编号非法。1 l.257 \end{tikzpicture}

我能做什么？代码如下：

\begin{textblock}{0.2}(0.7,13)
    \begin{tikzpicture}[scale=5.3,cap=round,>=latex]
      \def\Radius{.5cm}

      \draw (0cm,0cm) circle[radius=\Radius];

      \begin{scope}[
        -{Stealth[round, length=8pt, width=8pt, bend]},
        shorten >=4pt,
        very thin,
      ]
        \draw (0.315cm, -0.38cm) arc(-40-3:-40+3:\Radius);
        \draw (-\Radius, 0) arc(180+3:180-3:\Radius);
      \end{scope}

      % draw the two points 
      \fill[radius=.7pt]
        (-40:\Radius) circle[] node[below right] {$x$}
        (-60:\Radius) circle[] node[below right] {$y$}
      ;

      \def\Item#1#2(#3:#4){%
        \path[
          decoration={
            text along path,
            text={#1},
            text align=center,
          },
          decorate,
        ]
          (#3:\Radius-#2) arc(#3:#4:\Radius-#2)
        ;
      }
      \Item R 2pt (180:-40)
      \Item E 1pt (180:300)

      \node[draw,circle] at (-0.4,0.6)(a) {1};
      \node[draw,circle] at (0.65,0.6)(b) {2};

    \end{tikzpicture}
    \end{textblock}