pub fn process_vote_state_update<S: BuildHasher>(
    vote_account: &mut BorrowedAccount<'_>,
    slot_hashes: &[SlotHash],
    clock: &Clock,
    vote_state_update: VoteStateUpdate,
    signers: &HashSet<Pubkey, S>,
    feature_set: &FeatureSet
) -> Result<(), InstructionError>