% x
% \end{tcblisting}
%
-\usepackage{listings}
-\usepackage{tcolorbox}
+\ifx\havemjolisting\undefined
+\def\havemjolisting{1}
+
+
+\ifx\lstset\undefined
+ \usepackage{listings}
+\fi
+
+\ifx\tcbuselibrary\undefined
+ \usepackage{tcolorbox}
+\fi
% Tell tcolorbox to use ``listings'' within the boxes.
\tcbuselibrary{listings}
left=2em,%
listing options={language=sage,style=sage},%
listing file=sage_listings/#1.listing}}
+
+
+\fi