FkReference example

$field instanceof FkField => $field->getReferenceDefinition()->getEntityName(),
                        $field instanceof IdField => $entity,
                        default => null
                    };

                    if ($ref === null) {
                        continue;
                    }

                    $resolver = (string) $value['resolver'];

                    $row[$key] = $reference = new FkReference($value['value']);

                    $map[$resolver][] = $reference;
                }

                if (\is_array($value)) {
                    $field = $definition->getField($key);

                    if (!$field instanceof AssociationField) {
                        continue;
                    }