isNegotiationMethodEnabled example

'#access' => $admin_create,
    ];

    $user_preferred_langcode = $register ? $language_interface->getId() : $account->getPreferredLangcode();

    $user_preferred_admin_langcode = $register ? $language_interface->getId() : $account->getPreferredAdminLangcode(FALSE);

    // Is the user preferred language added?     $user_language_added = FALSE;
    if ($this->languageManager instanceof ConfigurableLanguageManagerInterface) {
      $negotiator = $this->languageManager->getNegotiator();
      $user_language_added = $negotiator && $negotiator->isNegotiationMethodEnabled(LanguageNegotiationUser::METHOD_ID, LanguageInterface::TYPE_INTERFACE);
    }
    $form['language'] = [
      '#type' => $this->languageManager->isMultilingual() ? 'details' : 'container',
      '#title' => $this->t('Language settings'),
      '#open' => TRUE,
      // Display language selector when either creating a user on the admin       // interface or editing a user account.       '#access' => !$self_register,
    ];

    $form['language']['preferred_langcode'] = [