code: public function relatedResource($resourceType, $id, $relationshipKey, $meta = null, array $queryParams = [])
      {
          return $this->factory->createLink(
              $this->urls->relatedResource($resourceType, $id, $relationshipKey, $queryParams),
              $meta,
              true
          );
      }
docs: Get a link to a resource object's related resource.
  
  @param $resourceType
  @param $id
  @param $relationshipKey
  @param array|object|null $meta
  @param array $queryParams
  @return LinkInterface