/**
  * Updates a field value, only if the field is translatable.
  *
  * @param string $field_name
  *   The name of the field.
  * @param mixed $value
  *   The field value to be set.
  */
 protected function setFieldOnlyIfTranslatable($field_name, $value)
 {
     if ($this->translation->getFieldDefinition($field_name)->isTranslatable()) {
         $this->translation->set($field_name, $value);
     }
 }