anchor.diff:  %% @doc make use of some other storage backend.
   
   -module(nebula2_db).
  +
  +-ifdef(TEST).
  +-include_lib("eunit/include/eunit.hrl").
  +-include("nebula2_test.hrl").
  +-endif.
   
   -include("nebula.hrl").
   %% ====================================================================
  
positive.code: 
  %% @doc Check for the availability of the metadata backend.
  -spec nebula2_db:available(pid()) -> boolean().
  available(Pid) ->
      {ok, Mod} = application:get_env(nebula2, cdmi_metadata_module),
      Mod:available(Pid).
      
  %% @doc Create an object.
  
negative.code:              object_oid(),      %% Oid
               map()              %% Data to store
              ) -> ok | {error, term()}.
  update(Pid, Oid, Data) when is_pid(Pid); is_binary(Oid); is_map(Oid) ->
      ?nebMsg("Entry"),
      {ok, Mod} = ?GET_ENV(nebula2, cdmi_metadata_module),
      Data2 = jsx:encode(Data),
      case Mod:update(Pid, Oid, Data2) of
          ok ->
              nebula2_utils:set_cache(Data),
              ok;
  