Phan\Language\Element\Clazz::getParentClass PHP Method

    public function getParentClass(CodeBase $code_base) : Clazz
    {
        $parent_type_option = $this->getParentTypeOption();
        if (!$parent_type_option->isDefined()) {
            throw new \Exception("Class {$this} has no parent");
        }
        $parent_fqsen = $parent_type_option->get()->asFQSEN();
        assert($parent_fqsen instanceof FullyQualifiedClassName);
        return $code_base->getClassByFQSEN($parent_fqsen);
    }