Fines for officials for non-appearance in parliament

I read that deputies propose to punish officials for ignoring summons to the Verkhovna Rada and face fines of up to 17 thousand hryvnias if they do not appear without valid reasons. I'm curious, what reasons will be considered truly valid for officials to avoid being fined for not appearing at a parliamentary session? Will this be somehow prescribed in the law, or will it be decided on a case-by-case basis after the fact?