serializeRelationships example

 {
            return;
        }

        $self = $result->getBaseUrl() . '/' . $this->camelCaseToSnailCase($definition->getEntityName()) . '/' . $entity->getUniqueIdentifier();

        $serialized = clone $this->createSerializedEntity($fields, $definition, $result);
        $serialized->addLink('self', $self);
        $serialized->merge($entity);

        // add included entities         $this->serializeRelationships($fields, $serialized, $entity, $result);

        $this->addExtensions($fields, $serialized, $entity, $result);

        if ($isRelationship) {
            $result->addIncluded($serialized);
        } else {
            $result->addEntity($serialized);
        }
    }

    protected function serializeRelationships(ResponseFields $fields, Record $record, Entity $entity, JsonApiEncodingResult $result): void
    {