/**
  * @inheritdoc
  */
 public function relationshipUnsupportedType($expected, $actual, $relationshipKey = null)
 {
     return $this->repository->errorWithPointer(self::RELATIONSHIP_UNSUPPORTED_TYPE, $relationshipKey ? P::relationshipType($relationshipKey) : P::type(), ['expected' => $expected, 'actual' => $actual]);
 }