Unused variable & t() calls should be avoided in classes issue

$ phpcs --standard=Drupalpractice --extensions=php,module,inc,install,test,profile,theme,css,info,txt,md,yml vbo_export/
Xdebug: [Step Debug] Time-out connecting to debugging client, waited: 200 ms. Tried: localhost:9000 (through xdebug.client_host/xdebug.client_port) :-(

FILE: C:\Users\SI-001\Downloads\vbo_export\src\Plugin\Action\VboExportBase.php
------------------------------------------------------------------------------
FOUND 0 ERRORS AND 1 WARNING AFFECTING 1 LINE
------------------------------------------------------------------------------
200 | WARNING | Unused variable $rand.
------------------------------------------------------------------------------

FILE: C:\Users\SI-001\Downloads\vbo_export\src\Plugin\Action\VboExportXlsx.php
-----------------------------------------------------------------------------------------------------------------------------------------
FOUND 0 ERRORS AND 1 WARNING AFFECTING 1 LINE
-----------------------------------------------------------------------------------------------------------------------------------------
65 | WARNING | t() calls should be avoided in classes, use \Drupal\Core\StringTranslation\StringTranslationTrait and $this->t() instead
-----------------------------------------------------------------------------------------------------------------------------------------

Time: 449ms; Memory: 8MB