How do I unindent?

[sickerin]

I'm not able to C-u - 4 C-x TAB. Negative value after C-u
https://www.emacswiki.org/emacs/IndentingText

[sickerin]

@kpe any suggestions on what to do. thanks! Like I know the reason is that the emacs codermirror doesn't have the shift-tab option, and only auto-indent is enabled. But how do you get around this? Perhaps, enabling a json like interface in advance settings where you can add extra keys or modify editor settings would be nice. Would you be okay if I tried to implement that and submit a pull request.