How to make a matrix with \llparenthesis and \rrparenthesis?

Question

I have the following document:

\documentclass{article}
 \usepackage{ stmaryrd }
 \usepackage{amsmath}
 \begin{document}
$\left\llparenthesis\!\!\!\left\llparenthesis\!
\begin{matrix}
1\\2\\3
\end{matrix}
\!\right\rrparenthesis\!\!\!\right\rrparenthesis
$
\end{document}

which provides the following:

How do I change the code to provide both brackets as long as the numbers 1, 2 and 3?

Answer 1

The font does not supply extensable ⦇ so you can not use \left or \right.

If you really want to fake this, you could do something like

\documentclass{article}
 
 \usepackage{amsmath}

 \begin{document}
$\left(\mkern-1.5mu\vrule width.7pt\mkern2mu
\begin{matrix}
1\\2\\3
\end{matrix}
\mkern2mu\vrule width .7pt\mkern-1.5mu\right)
$
\end{document}