Utilisation de tcolorbox

\documentclass[12pt,a4paper]{book}
\usepackage{lmodern}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{xcolor}
\usepackage{amsthm}
\usepackage{tcolorbox}
\usepackage{lmodern}
\usepackage[T1]{fontenc}
\usepackage[tikz]{bclogo}
\usepackage{amsfonts,amssymb}
\usepackage{enumitem, pifont}
\usepackage{fancyhdr}
\usepackage{pstricks}
\usepackage{fancybox}
\usepackage{lipsum}
\usepackage{cleveref}
\usepackage{varioref}
\usepackage{varwidth}
\usepackage{amsthm}
\usepackage{pgfkeys}
\tcbuselibrary{skins, theorems, xparse}
\usepackage{tcolorbox}
\tcbuselibrary{skins, theorems}
\usetikzlibrary{patterns}
\tcbuselibrary{breakable}
\usepackage{varwidth} 
\begin{document}
 
\newtcolorbox{mybox}[2][]{enhanced,
 
before skip=2mm,after skip=2mm,
 
colback=black!5,colframe=black!50,boxrule=0.2mm,
 
attach boxed title to top left={xshift=1cm,yshift*=1mm-\tcboxedtitleheight},
 
varwidth boxed title*=-3cm,
 
boxed title style={frame code={
 
\path[fill=tcbcolback!30!black]
 
([yshift=-1mm,xshift=-1mm]frame.north west)
 
arc[start angle=0,end angle=180,radius=1mm]
 
([yshift=-1mm,xshift=1mm]frame.north east)
 
arc[start angle=180,end angle=0,radius=1mm];
 
\path[left color=tcbcolback!60!black,right color=tcbcolback!60!black,
 
middle color=tcbcolback!80!black]
 
([xshift=-2mm]frame.north west) -- ([xshift=2mm]frame.north east)
 
[rounded corners=1mm]-- ([xshift=1mm,yshift=-1mm]frame.north east)
 
-- (frame.south east) -- (frame.south west)
 
-- ([xshift=-1mm,yshift=-1mm]frame.north west)
 
[sharp corners]-- cycle;
 
},interior engine=empty,
 
},
 
fonttitle=\bfseries,
 
title={#2},#1}
 
\begin{mybox}[colbacktitle=green]{My title}
 
\lipsum[2]
 
\end{mybox}
 
\begin{mybox}[colbacktitle=red]{My title}
 
\lipsum[3]
 
\end{mybox}
 
My title
 
\end{document}