code: @SuppressWarnings("unchecked")
    protected AppendRequest buildAppendEmptyRequest(MemberState member) {
      Entry prevEntry = getPrevEntry(member);
  
      ServerMember leader = context.getLeader();
      return AppendRequest.builder()
        .withTerm(context.getTerm())
        .withLeader(leader != null ? leader.id() : 0)
        .withLogIndex(prevEntry != null ? prevEntry.getIndex() : 0)
        .withLogTerm(prevEntry != null ? prevEntry.getTerm() : 0)
        .withEntries(Collections.EMPTY_LIST)
        .withCommitIndex(context.getCommitIndex())
        .withGlobalIndex(context.getGlobalIndex())
        .build();
    }
docs: Builds an empty AppendEntries request.
  <p>
  Empty append requests are used as heartbeats to followers.