Function interpret_selection 

pub fn interpret_selection<'a, This>(
    alg: &This,
    formats: &'a [Format],
    selection: &FormatSelection,
) -> Option<Vec<&'a Format>>
where
    This: FormatPredicateMatchAlg<Predicate = FormatPredicate, Format = Format>,

Interprets one reified selection program against a preference-ordered catalog.

This is the canonical meaning of the reified syntax; an interpreter that chose those sorts states FormatSelectionApplyAlg by delegating here.