public Map<String, ClassicGroupMember> notYetRejoinedMembers() {
        Map<String, ClassicGroupMember> notYetRejoinedMembers = new HashMap<>();
        members.values().forEach(member -> {
            if (!member.isAwaitingJoin()) {
                notYetRejoinedMembers.put(member.memberId(), member);
            }
        });
        return notYetRejoinedMembers;
    }
@return members who have yet to rejoin during the
        join group phase.
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/classic/ClassicGroup.java