Function is_swap_index_key 

fn is_swap_index_key(key: &str) -> bool

Whether key names a swap index as SwapIndex::code writes it: a registered fixed-versus-IBOR swap template’s code in its registered casing, a hyphen, and the tenor in its largest exact unit ("EUR-EURIBOR-6M-IRS-10Y"). A CMS coupon reads its print under that key, so membership is checked through the template registry, as a rate index’s is through the index registry.