Function mz_expr::canonicalize::get_canonicalizer_map

pub fn get_canonicalizer_map(
    equivalences: &Vec<Vec<MirScalarExpr>>,
) -> BTreeMap<MirScalarExpr, MirScalarExpr>

For each equivalence class, it finds the simplest expression, which will be the canonical one. Returns a Map that maps from each expression in each equivalence class to the canonical expression in the same equivalence class.