anchor.diff:  %%   `{error, Reason}' if the user didn't select the kind of entity 
   %%   expected; or `{ok, term()' when a valid focus of interest has been
   %%   selected.
  -%%  ```pre_cond_check(Args::#args{})
  +%%  ```check_pre_cond(Args::#args{})
   %%       ===> ok | {error, Reason}'''
   %%   This function checks whether the pre-conditions of the refactoring 
   %%   hold, and returns `ok' if the pre-condition checking passes, otherwise
  
positive.code:               {ok, [{filename(), filename(), syntaxTree()}]} |
                {error, term()}).
  apply_changes(Module, Args, CandsNotToChange) ->
      wrangler_gen_refac_server:add_value({self(), {false, CandsNotToChange}}),
      case apply(Module, transform, [Args]) of
          {ok, Res} ->
              wrangler_gen_refac_server:delete_value(self()),
              refac_write_file:write_refactored_files(
                Res, 'emacs', Args#args.tabwidth, "");
          {error, Reason} ->
              wrangler_gen_refac_server:delete_value(self()),
              {error, Reason}
      end.
  
  
negative.code: select_focus(Module, Args) ->
      apply(Module, select_focus, [Args]).
  
  -spec(check_pre_cond(Module::module(), Args::[term()]) ->
               ok | {error, term()}).
  check_pre_cond(Module, Args) ->
      apply(Module,check_pre_cond, [Args]).
  
  -spec(selective(Module::module()) ->
               boolean()).
  