protected function configure_user_columns($table) {
        $table->column_suppress('picture');
        $table->column_suppress('fullname');
        $extrafields = get_extra_user_fields($this->context);
        foreach ($extrafields as $field) {
            $table->column_suppress($field);
        }

        $table->column_class('picture', 'picture');
        $table->column_class('lastname', 'bold');
        $table->column_class('firstname', 'bold');
        $table->column_class('fullname', 'bold');
    }