Also avoid the first person here, it'll become something like:

````rst
First of all, the class loader is loaded manually using a ``require`` statement,
since there is no autoload mechanism yet. With the
:method:`Symfony\Component\ClassLoader\Psr4ClassLoader::addPrefix` call,
you tell the class loader where to look for classes with the
``Symfony\Component\Yaml\`` namespace prefix. After registering the autoloader,
the Yaml component is ready to use.
````