\documentclass{article}
\usepackage{circus}
\usepackage{stateflow}
\begin{document}

\begin{zsection}\\
\SECTION calc\_th \parents basic\_toolkit
\end{zsection}\\
%
\begin{axdef}
calc\_th:(\real \cross \real) \fun (\real \cross \real)
\end{axdef}

\end{document}