public static function load($mode)
    {
		if (!is_string($mode)){
			throw new InvalidArgumentException('Try to load an irregular mode in the context. The mode must be a string, ' . gettype($mode) . ' given.');
		}
    	else if (empty($mode)){
    		throw new InvalidArgumentException('Cannot load an empty mode in the context.');
    	}
    	
    	if(!in_array($mode, self::$current)){
    		self::$current[] = $mode;
    	}
    }