src/Normalizer/EntityReferenceItemNormalizer.php
public function getUuid($data) {

    if (isset($data['uuid'])) {
      $uuid = $data['uuid'];
      // The value may be a nested array like $uuid[0]['value'].
      if (is_array($uuid) && isset($uuid[0]['value'])) {
        $uuid = $uuid[0]['value'];
      }
      return $uuid;
    }
  }
public function getUuid($data) {

    if (isset($data['uuid'])) {
      $uuid = $data['uuid'];
      // The value may be a nested array like $uuid[0]['value'].
      if (is_array($uuid) && isset($uuid[0]['value'])) {
        $uuid = $uuid[0]['value'];
      }
      return $uuid;
    }
  }
{@inheritdoc}