How to define custom code listing?

I have the following custom listing but it throws error for lstset part that the keys are undefined. Any ideas how to fix this?

\documentclass{llncs}\pagestyle{plain}\usepackage[utf8]{inputenc}\usepackage{listings}\lstdefinelanguage{Sage}[]{Python}{morekeywords={False,sage,True},sensitive=true}\lstset{  frame=none,  showtabs=False,  showspaces=False,  showstringspaces=False,  commentstyle={\ttfamily\color{dgreencolor}},  keywordstyle={\ttfamily\color{dbluecolor}\bfseries},  stringstyle={\ttfamily\color{dgraycolor}\bfseries},  language=Sage,  basicstyle={\fontsize{10pt}{10pt}\ttfamily},  aboveskip=0.3em,  belowskip=0.1em,  numbers=left,  numberstyle=\footnotesize}\definecolor{dblackcolor}{rgb}{0.0,0.0,0.0}\definecolor{dbluecolor}{rgb}{0.01,0.02,0.7}\definecolor{dgreencolor}{rgb}{0.2,0.4,0.0}\definecolor{dgraycolor}{rgb}{0.30,0.3,0.30}\newcommand{\dblue}{\color{dbluecolor}\bf}\newcommand{\dred}{\color{dredcolor}\bf}\newcommand{\dblack}{\color{dblackcolor}\bf}\begin{document}\section{Test}A code example:\begin{lstlisting}sage: R.<x> = ZZ[]sage: type(R.an_element())<type 'sage.rings...Polynomial_integer_dense_flint'>sage: R.<x,y> = ZZ[]sage: type(R.an_element())<type 'sage.rings...MPolynomial_libsingular'>sage: R = PolynomialRing(ZZ, 'x', implementation='NTL')sage: type(R.an_element())  # this is a comment<type 'sage.rings...Polynomial_integer_dense_ntl'>sage: def abc():...       """...       This should be a very long comment....       That should span multiple lines....       To illustrate what colour Sage comments look like....       To get a feel for the color when rendered using LaTeX....       """...       return 2\end{lstlisting}\end{document}