protected function getClasses()
    {

        $classes = config('slack-output.stats.classes');

        //force classes to have the right format
        $sanitized_classes = [ ];
        foreach ($classes as $classes_name => $constraints) {
            //check constraints are supplied, if not, correct
            //the classes name with the right value
            if (is_int($classes_name)) {
                $classes_name = $constraints;
                $constraints  = [ ];
            }
            $sanitized_classes[$classes_name] = $constraints;
        }

        return $sanitized_classes;
    }