private static function setDefaults() {
            if (!self::$defaults) {
                self::$defaults =
                    [self::CFG_CSS_PATH           => __DIR__ . DIRECTORY_SEPARATOR . '..' . DIRECTORY_SEPARATOR . '..' .
                                                     DIRECTORY_SEPARATOR . 'error.min.css',
                     self::CFG_TRACE_MAX_DEPTH    => 50,
                     self::CFG_BACKGROUND         => 'default',
                     self::CFG_FOREGROUND_NOTICE  => 'cyan',
                     self::CFG_FOREGROUND_WARNING => 'yellow',
                     self::CFG_FOREGROUND_ERROR   => 'red',
                     self::CFG_FORCE_HTML         => false];
            }
        }