magento2 – Adding plugin on tinymce

So i follow this tutorial ->

And everything works so far if i remove this line of code

ed.contentCSS = [ed.settings.magentoPluginsOptions._object.Addfourcolumnbox.css];

But if i add it i get an error that say this

Failed to initialize plugin: Addfourcolumnbox TypeError: Cannot read property 'Addfourcolumnbox' of undefined
at t.<computed>.t.<computed>.init

So i have tried everything to fix it, but nothing works, so i hope somebody else have dealt with the same problem before me and found a answer to it.