Import package from plugin code

How do I import missing (java) package when I PsiReference to the package I want to import. I can also get the PsiClass for the reference with ImportClassFix, but executing doFix() on it doesnt do anything to the underaying document.

 (I'm creating neovim plugin which integrates Intellij Idea functionality to neovim: https://github.com/vhakulinen/neovim-intellij-complete)