How-to-deprecate.md

 So you want to deprecate something in OTB? Follow the guide:
 
-## A C++ class
+#### A C++ class
 
 In the doxygen documentation of the class, add the `\deprecated` keyword.
 
 In the class declaration, use the `[[deprecated]]` attribute. If the class declaration already has an export macro, use the macro `_DEPRECATED_EXPORT`.
 
-## A method of a C++ class
+#### A method of a C++ class
 
 Use the `[[deprecated]]` attribute.
 
-## A part of the Python API
+#### A part of the Python API
 
 TODO
 
-## An OTB application
+#### An OTB application
 
 Add the tag deprecated:
 
@@ -22,11 +22,13 @@ Add the tag deprecated:
 AddDocTag(Tags::Deprecated);
 ```
 
-## An OTB module
+#### An OTB module
 
 Add the keyword `DEPRECATED` in the call to `otb_module()` macro in file `otb-module.cmake`
 
-## How to disable deprecated features when `OTB_USE_DEPRECATED=OFF`?
+#### How to disable deprecated features when `OTB_USE_DEPRECATED=OFF`?
+
+For an example, see [this MR](https://gitlab.orfeo-toolbox.org/orfeotoolbox/otb/merge_requests/236/diffs)
 
 * If you deprecate a whole module, it will be disabled during configure step.
 * If you want to deprecate a C++ class and the associated tests: use variable `OTB_USE_DEPRECATED` to protect the inclusion of this class in `src/CMakeLists.txt` and `test/CMakeLists.txt`