<html><head><meta name="color-scheme" content="light dark"></head><body><pre style="word-wrap: break-word; white-space: pre-wrap;">\begin{sequencediagram}
  \newthread{t1}{:Thread1}
  \newthread[gray]{t2}{:Thread2}

  \begin{callself}{t1}{loop}{}
  \end{callself}

  \prelevel\prelevel

  \begin{callself}{t2}{loop}{}
  \end{callself}
\end{sequencediagram}
</pre></body></html>