SilverStripe\SiteConfig\SiteConfig:
  extensions:
    - Site\Extensions\SiteConfigExtension
    - Site\Extensions\SocialExtension

SilverStripe\SiteTree\SiteTree:
  extensions:
    - SiteTreeExtension

SilverStripe\Blog\Model\BlogPost:
  extensions:
    - Site\Extensions\BlogPostExtension

SilverStripe\Core\Injector\Injector:
  SilverStripe\UserForms\Model\UserDefinedForm:
    class: Site\Extensions\CMSMain_HiddenClass