findOutIfNamespaceIsComposerLoaded.php

<?php

$namespace = 'aBase\\';
$classes = get_declared_classes();
$keys = preg_grep('/ComposerAutoloaderInit*/', $classes);
foreach ($keys as $composerLoader) {
    if (method_exists($composerLoader, 'getLoader')) {
        $composer = $composerLoader::getLoader();
        if($composer && $composer->getPrefixesPsr4()){
            if(array_key_exists($namespace, $composer->getPrefixesPsr4())){
                $abase_composer = $composerLoader::getLoader();
            }
        }
    }
}