Improvement: "yapf: enable/disable" alternative heuristic

I just read this article: http://journal.stuffwithstuff.com/2015/09/08/the-hardest-program-ive-ever-written/

The dart formatter uses a simple heuristic to know when to (or not to) reformat data structure blocks - comments (but not explicit enable/disable).

I think their example is pretty clear: https://github.com/dart-lang/dart_style#why-does-the-formatter-mess-up-my-collection-literals

I find this preferable to adding formatter-specific tags to my source code.