Function match_reason 

pub fn match_reason<'a>(
    view: &SavedView,
    dataset: impl Into<Dataset<'a>>,
    schema: &Schema,
) -> Option<MatchReason>

The strongest criterion of the view’s that fits this file, or None when none does. This is the same test criteria_match gates on, kept in one place so the list’s “why it matches” annotation can never disagree with what V and auto-apply do.