ast.parse, ast.dump, but with comment preservation?

[samue...@gmail.com]

> > PS: Library is https://github.com/SamuelMarks/cdd-python (might relicense with CC0… anyway too early for others to use; wait for the 0.1.0 release ;])
Ended up writing my own CST and added it to that library of mine (link above).

My target is adding/removing/changing of: docstrings, function return types, function arguments, and Assign/AnnAssign. All but the last are now implemented.

I was careful not to replace code elsewhere in my codebase, so everything except my new CST code (in its own files) stays, and everything else works exclusively with the builtin `ast` module as before.