core-bundle/src/Resources/contao/library/Contao/ClassLoader.php
public static function addNamespace($name)
	{
		@trigger_error('Using ClassLoader::addNamespace() has been deprecated and will no longer work in Contao 5.0.', E_USER_DEPRECATED);

		if (\in_array($name, self::$namespaces))
		{
			return;
		}

		array_unshift(self::$namespaces, $name);
	}
public static function addNamespace($name)
	{
		@trigger_error('Using ClassLoader::addNamespace() has been deprecated and will no longer work in Contao 5.0.', E_USER_DEPRECATED);

		if (\in_array($name, self::$namespaces))
		{
			return;
		}

		array_unshift(self::$namespaces, $name);
	}
Add a new namespace

@param string $name The namespace name

@deprecated Deprecated since Contao 4.2, to be removed in Contao 5.