anchor.diff:      map | 
       log_level |
       map() |                     % Allow for nested objects
  -    list() |                    % First mathing option is used
  +    list() |                    % First matching option is used
       syntax_fun() |
       '__defaults' |              % Defaults for this level
       '__mandatory'.              % Mandatory fields (only root level)
  
positive.code:     path :: binary(),
      defaults :: map(),
      mandatory :: [binary()],
      opts :: map()
  }).
  
  
  
negative.code:     fun((Val::term()) -> syntax_fun_out()) |
      fun((Key::atom(), Val::term()) -> syntax_fun_out()) |
      fun((Key::atom(), Val::term(), fun_ctx()) -> syntax_fun_out()).
  
  
  -type syntax_fun_out() ::
      ok | 
  