pub(crate) fn select_committee_inner<AccountId: Clone + PartialEq>(
    current_session: SessionIndex,
    reserved_seats: usize,
    non_reserved_seats: usize,
    non_reserved_finality_seats: usize,
    reserved: &[AccountId],
    non_reserved: &[AccountId]
) -> Option<SessionCommittee<AccountId>>