overleaf/services/clsi/test/acceptance/fixtures/examples/gnuplot/main.tex

\documentclass{article}
\usepackage{pgfplots}
\usepackage{nopageno}

\pgfplotsset{compat=newest}

\begin{document}

\begin{tikzpicture}
  \begin{axis}
    \addplot +[no markers,
      raw gnuplot,
      thick,
      empty line = jump
      ] gnuplot {
      set contour base;
      set cntrparam levels discrete 0.003;
      unset surface;
      set view map;
      set isosamples 500;
      splot x**3-3*x+3-y**2;
    };
  \end{axis}
\end{tikzpicture}

\end{document}