https://api.drupal.org/api/drupal/core%21modules%21language%21tests%21src%21Functional%21LanguageBreadcrumbTest.php/class/hierarchy/LanguageBreadcrumbTest/10
LanguageBreadcrumbTest | Drupal API
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https://api.drupal.org/api/drupal/core%21modules%21language%21tests%21src%21Functional%21LanguageBreadcrumbTest.php/property/LanguageBreadcrumbTest%3A%3AdefaultTheme/8.9.x
LanguageBreadcrumbTest::$defaultTheme | Drupal API
drupalapi