This is designed as a validator designed around current Arena standards -- to be used to validate and confirm whether or not a platform's generated export format meets Arena's specs (as Arena has no officially published specs, I've tried to determine varied test cases including decks with both commanders and companions).
- There are four possible sections, that appear in the following sequence: Commander, Companion, Deck, Sideboard.
- The section title is the first line of each section.
- Blank lines are inserted after each section.
- If a line begins with an integer, it's a card. If it begins with anything else, it's a Section title.