View file core/libs/s3/vendor/composer/installers/src/Composer/Installers/Plugin.php

<?php

namespace Composer\Installers;

use Composer\Composer;
use Composer\IO\IOInterface;
use Composer\Plugin\PluginInterface;

class Plugin implements PluginInterface
{

    public function activate(Composer $composer, IOInterface $io)
    {
        $installer = new Installer($io, $composer);
        $composer->getInstallationManager()->addInstaller($installer);
    }
}