https://api.drupal.org/api/drupal/core%21modules%21block_content%21src%21Plugin%21migrate%21source%21d7%21BlockCustomTranslation.php/class/BlockCustomTranslation/11.x
class BlockCustomTranslation | Drupal API
classdrupalapi
https://api.drupal.org/api/drupal/core%21modules%21block_content%21src%21Plugin%21migrate%21source%21d7%21BlockCustomTranslation.php/function/BlockCustomTranslation%3A%3Afields/11.x
function BlockCustomTranslation::fields | Drupal API
functionfieldsdrupalapi