anchor.diff:  
   % -compile([export_all]).
   % -define(TEST, 1).
  -
   -ifdef(TEST).
   -include_lib("eunit/include/eunit.hrl").
   
  
positive.code:             Spec, map),
  
      {ok, [{field13, [a, b, '3']}], []} = parse_config(#{field13 => [a, "b", 3]}, Spec),
      ok.
  
  
  
  
  
  parse_fun(field10, data, _Opts) ->
  
negative.code:             ok | {ok, term()} | {opts, [{atom(), term()}]} | error).
  
  -type parse_opt() ::
      opt() | {list, opt()} | {update, map|list, MapOrList::atom(), Key::atom(), opt()}.
  
  -type parse_spec() :: #{ atom() => parse_opt()}.
  
  