You'd just wrap it:

```php
class MyHydrator implements HydratorInterface
{
    public function __construct()
    {
        $this->wrapped = new ClassMethods();
        $this->wrapped->addStrategy('whatever', new SomeStrategy);
    }
    public function hydrate(array $data, $object)
    {
        return $this->wrapped->hydrate($data, $object);
    }

    public function extract($object)
    {
        return $this->wrapped->extract($object);
    }
}
```