anchor.diff:  gc_blacklist() ->
       gen_server:call(?MODULE, gc_blacklist).
   
  +-spec gc_blacklist([node()]) -> 'ok'.
  +gc_blacklist(Nodes) ->
  +    gen_server:cast(?MODULE, {gc_blacklist, Nodes}).
  +
  +-spec get_hosted_tags(host()) -> {'ok', [tagname()]} | {'error', term()}.
  +get_hosted_tags(Host) ->
  +    gen_server:call(?MODULE, {get_hosted_tags, Host}).
  +
   -spec choose_write_nodes(non_neg_integer(), [node()]) -> {'ok', [node()]}.
   choose_write_nodes(K, Exclude) ->
       gen_server:call(?MODULE, {choose_write_nodes, K, Exclude}).
  
positive.code: -export([get_tags/1,
           get_nodeinfo/1,
           get_read_nodes/0,
           gc_blacklist/0,
           gc_blacklist/1,
           choose_write_nodes/2,
  
negative.code: -spec update_tag_cache(gb_set()) -> 'ok'.
  update_tag_cache(TagCache) ->
      gen_server:cast(?MODULE, {update_tag_cache, TagCache}).
  
  %% ===================================================================
  %% gen_server callbacks
  