protected function get_mimetype_from_filename($filename) {
        $mimetype = 'application/unknown';
        $types = core_filetypes::get_types();
        $fileextension = '.bin';
        if (strpos($filename, '.') !== false) {
            $fileextension = substr($filename, strrpos($filename, '.') + 1);
        }

        if (isset($types[$fileextension])) {
            $mimetype = $types[$fileextension]['type'];
        }
        return $mimetype;
    }