lib/Twig/Loader/Themes.php
protected function prepareName($name)
    {
        $name = preg_replace('#/{2,}#', '/', strtr($name, '\\', '/'));
        if (isset($name[0]) && static::NP_PREFIX != $name[0]) {
            $name = static::NP_PREFIX.$this->theme.'/'.$name;
        }

        return $name;
    }
protected function prepareName($name)
    {
        $name = preg_replace('#/{2,}#', '/', strtr($name, '\\', '/'));
        if (isset($name[0]) && static::NP_PREFIX != $name[0]) {
            $name = static::NP_PREFIX.$this->theme.'/'.$name;
        }

        return $name;
    }
Prepend theme namespace if namespace not set.

@param string $name
@return string