Missing the most important one: Provide type/function annotations. I'm also skeptical to all the recommendations about opening up the internals, getting out of

Missing the most important one: Provide type/function annotations. I'm also skeptical to all the recommendations about opening up the internals, getting out of the abstractions and providing replaceable hooks for everything. This can create premature abstractions for every conceivable hook and exposing internals will give you a backwards compatibility maintenance hell when you have to be compatible with internal details you didn't think people depended on.