anchor.diff:      %% persisted seq no should not be possible here
       {ok, SeqNo} = ns_memcached:get_vbucket_high_seqno(Bucket, VBucket),
       {reply, SeqNo, State};
  -handle_call({get_tap_docs_estimate, _VBucketId, _TapName} = Req, From, State) ->
  -    handle_call_via_servant(
  -      From, State, Req,
  -      fun ({_, VBucketId, TapName}, #state{bucket_name = Bucket}) ->
  -              ns_memcached:get_tap_docs_estimate(Bucket, VBucketId, TapName)
  -      end);
   handle_call({get_tap_docs_estimate_many_taps, _VBucketId, _TapName} = Req, From, State) ->
       handle_call_via_servant(
         From, State, Req,
  
positive.code: 
  do_servant_call(Server, Request) ->
      get_servant_call_reply(initiate_servant_call(Server, Request)).
  
  get_tap_docs_estimate(Bucket, SrcNode, VBucket, TapName) ->
      RV = do_servant_call({server_name(Bucket), SrcNode},
                           {get_tap_docs_estimate, VBucket, TapName}),
      {ok, _} = RV,
      RV.
  
  -spec get_tap_docs_estimate_many_taps(bucket_name(), node(), vbucket_id(), [binary()]) ->
                                               [{ok, {non_neg_integer(), non_neg_integer(), binary()}}].
  
negative.code:          complete_flush/3,
           get_replication_persistence_checkpoint_id/4,
           wait_checkpoint_persisted/5,
           get_tap_docs_estimate_many_taps/4,
           get_mass_tap_docs_estimate/3,
           get_dcp_docs_estimate/4,
  