What does the mime type "gagt / sdf" mean in android when creating an intent

Question

Intent fileintent = new Intent(Intent.ACTION_GET_CONTENT);
    fileintent.setType("gagt/sdf");
    try {
        startActivityForResult(fileintent, PICKFILE_RESULT_CODE);
    } catch (ActivityNotFoundException e) {
        Log.e("tag", "No activity can handle picking a file. Showing alternatives.");
    }

This code segment seems to magically start the file collector.

I looked at the Android developer file, but no explanation was found.

Why does it work?