# How can you change the appearance of a line (edge) with a tikz graph drawing algorithm written in Lua?

In my graph drawing algorithm (written in Lua for LuaLaTeX), I'd like to change a solid line to a dashed line. I use a Digraph with some vertices and arcs between them. On page 499 of the Tikz & PGF manual, it talks about a field generated_options that an Arc has. The generated_options will be passed to its edges, which in turn will be passed down to the display layer. I thought it would be as simple as:

arc.generated_options = {{key = "dashed", value="true"}}


But this doesn't do anything. What am I missing here?

I can make the line dashed in the \graph:

(the tree layout is used here, but I'm using my own layout)

\documentclass[11pt,a4paper]{article}
\usepackage{tikz}
\usetikzlibrary{graphs,graphdrawing}
\usegdlibrary{trees}

\begin{document}
\begin{tikzpicture}[tree layout]
\graph{
"Start"[rectangle, draw] --[dashed]
"End"[rectangle, draw]
};
\end{tikzpicture}
\end{document}


but I'd like my Lua algorithm to change it to dashed instead. Does anyone know how to do this?