Sometimes, when I edit a large file, I like to focus only on a part of the document and not all of it.

Is it possible to create a sort of fold that wrap a part of the document (e.g. the current function/paragraph) so the focus is narrowed on that ?

The idea would be to produce something like this:

+ --- the fold --- >

// Interesting stuff, i.e. a cat
// 
//   |\      _,,,---,,_
//  /,`.-'`'    -.  ;-;;,_
// |,4-  ) )-,_..;\ (  `'-'
// '---''(_/--' `-'\_)
//
 
+ --- the fold --- >