\usepackage{xcolor}
\usepackage{listings}

\lstset{
    basicstyle=\ttfamily,
    numbers=none,
    keywordstyle=\color[rgb]{0.13,0.29,0.53}\bfseries,
    stringstyle=\color[rgb]{0.31,0.60,0.02},
    commentstyle=\color[rgb]{0.56,0.35,0.01}\itshape,
    numberstyle=\footnotesize,
    stepnumber=1,
    numbersep=5pt,
    backgroundcolor=\color[RGB]{248,248,248},
    showspaces=false,
    showstringspaces=false,
    showtabs=false,
    tabsize=2,
    captionpos=b,
    breaklines=true,
    breakatwhitespace=true,
    breakautoindent=true,
    escapeinside={\%*}{*)},
    linewidth=\textwidth,
    basewidth=0.5em,
}

\usepackage{enumitem}
\setlistdepth{20}
\renewlist{itemize}{itemize}{20}
% maintain visual parity with the builtin list
\setlist[itemize]{labelsep=.5em}
% initially, use dots for all levels
\setlist[itemize]{label=$\cdot$}
% customize the first 3 levels
\setlist[itemize,1]{label=\textbullet}
\setlist[itemize,2]{label=$\circ$}
\setlist[itemize,3]{label=\textbullet}