pub type Invulnerables<T: Config> = StorageValue<_GeneratedPrefixForStorageInvulnerables<T>, Vec<T::AccountId>, ValueQuery>;
Any validators that may never be slashed or forcibly kicked. It’s a Vec since they’re easy to initialize and the performance hit is minimal (we expect no more than four invulnerables) and restricted to testnets.
Storage type is
StorageValue with value type
Vec < T :: AccountId >.