beamer add tag

It's a long time issue for me to toggle smoothly between `article/book/report` and `beamer/handout`.

After using [`beamerswitch`](, I discovered an efficient solution to do so. The problem is it's supposed to work only for `article` [(page 13, 9.4 Setting up modes)](


**Extension to `book` works**

Naively... I tried 

in the `beamerswitch.cls`, it actually works !

I can now use the `book` class in my new `JETswitch.cls` (with `\chapter`).


I tried then to extend that to `tufte-book` (I use often) and thanks to this [nice answer]( I understood I had to be careful when loading `tufte-book` with `beamerarticle`.

**Extension to `tufte-book` does not understant `\chapter`**

Strangely, the classe is loaded but `\chapter` is not understood

**My question**

What am I missing ?

Below the modified MWE provided with the package

%% This is file `beamerswitch-example.tex',
%% generated with the docstrip utility.
%% The original source files were:
%% beamerswitch.dtx  (with options: `example')
%% ----------------------------------------------------------------
%% beamerswitch --- Convenient mode selection in Beamer documents
%% Author:  Alex Ball
%% E-mail:
%% License: Released under the LaTeX Project Public License v1.3c or later
%% See:
%% ----------------------------------------------------------------

%\PassOptionsToClass{a4paper,12pt}{article}	 %<- works well 
%\PassOptionsToClass{a4paper,12pt}{book}	%<- works well 
%\documentclass[also={trans,handout,article}]{JETswitch} %<- 


\title{A demonstration of the \textsf{beamerswitch} class}
\subtitle{Testing features}
\author{Alex Ball}
\institute{University of Life}
\date{1 September 2016}
\subject{A LaTeX class}
\keywords{CTAN, literate programming}



%\mode<article>{\chapter{Chapter in book}}
%\mode<presentation>{\lecture{chap}{lecture in beamer}}

  This very brief demonstration shows how to use the \textsf{beamerswitch} class.
  It allows easy switching between four \textsf{beamer} modes:

\section{First section}

  \begin{frame}{Beamer modes}
      \item \textbf{beamer:} regular slides
      \item \textbf{trans:} slides suitable for printing on transparencies
      \item \textbf{handout:} slides suitable for printing on paper
      \item \textbf{article:} transcript, paper, notes or other article-style
        document based on the slides

  Notice how the text outside frames is only shown in article mode. Also,

\section{Second section}

  \begin{frame}{Features shown in this example}
      \item Different class options are passed to the \textsf{beamer} and
        \textsf{article} classes.
      \item The `trans' and `handout' versions do not have the intermediate
        slides used by the `beamer' version for uncovering content.
      \item The handout has three slides to a page with room for handwritten
        notes at the side, and is in black and white.

    \uncover<+->{See the source code of this example to see how it was done.}

  This PDF also has title and author information saved in the metadata (look
  at the properties in your PDF viewer).

  Happy {\LaTeX}ing!
%% Copyright (C) 2016-2020 by Alex Ball <>
%% End of file `beamerswitch-example.tex'.

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