Unable to exclude style files

[latvys]

I am trying to config bundle options so I can omit from bundling files in Frontend/_assets/Content folder. I've tried inserting "!FrontEnd/_assets/Content/**/*.{css,less}" in both bundle configs and bundle options, but it seems to not work.

var bundleOptions = { order: { styles: [ ... "!FrontEnd/_assets/Content/**/*.{css,less}", "Frontend/**/*.{css,less}" ] } };

module.exports = { bundle: { ... app: { styles: ["!FrontEnd/_assets/Content/**/*.{css,less}" "Frontend/**/*.{css,less}"], options: bundleOptions } }