lib/Twig/Loader/Themes.php
public function getCacheKey($name)
    {
        $name = $this->prepareName($name);
        return $this->theme . '::' . $this->fsloader->getCacheKey($name);
    }
public function getCacheKey($name)
    {
        $name = $this->prepareName($name);
        return $this->theme . '::' . $this->fsloader->getCacheKey($name);
    }
Add theme to file system loader cache key.
{@inheritdoc}