📑context/💡idea/blog #🏷️topic/code
https://stackoverflow.com/questions/1452934/what-is-the-meaning-of-xxx-in-code-comments
https://google.github.io/styleguide/cppguide.html#TODO_Comments
http://www.python.org/dev/peps/pep-0350
http://www.oracle.com/technetwork/java/javase/documentation/codeconventions-137265.html#395
original from old apache code?