anchor.diff:  
   sort_po_file(LC) ->
       LCPo = read_po_file(LC),
  -    SortedPo = lists:sort(fun({K1, _V1}, {K2, _V2}) -> K1 < K2 end, LCPo),
  +    SortedPo = lists:keysort(1, LCPo),
       write_po_file(LC, SortedPo, "Polish tool", "polish@polish.org").
  
positive.code:     end.
  
  update_po_files(DefaultPo, [LC|T]) ->
      LCPo = read_po_file(LC),
      check_no_duplicates_and_sorted(LCPo, LC),
      wash_po_file(LCPo, DefaultPo, LC),
      update_po_files(DefaultPo, T);
  update_po_files(_DefaultPo, []) ->
      ok.
  
  check_no_duplicates_and_sorted([], _LC) ->
      ok;
  
negative.code: 	true  -> 
  	    check_no_duplicates_and_sorted(KVs, K, LC);
  	false when K =:= PrevK -> 
  	    {error, io_lib:format("ERROR: Duplicated key found in ~s language."
  				   "Run polish:get_duplicated_keys(~s) "
  				   ", remove all the duplicated keys and"
  				   " run polish:update_po_files() again.",
  				   [LC, LC])};
  	false ->
  	    unsorted
      end;
  check_no_duplicates_and_sorted([], _PrevK, _LC) ->
      ok.
  
  wash_po_file(PoToWash, DefaultPo, LC) ->
      PoToWash1 = add_new_delete_old_keys(PoToWash, DefaultPo),
  