8 files declare their use of WarmerPluginBase in Warmer 2.x

CdnWarmer.php in modules/warmer_cdn/src/Plugin/warmer/CdnWarmer.php

EnqueueForm.php in src/Form/EnqueueForm.php

EntityWarmer.php in modules/warmer_entity/src/Plugin/warmer/EntityWarmer.php

HookImplementations.php in src/HookImplementations.php

QueueManager.php in src/QueueManager.php

SettingsForm.php in src/Form/SettingsForm.php

SitemapWarmer.php in modules/warmer_cdn/src/Plugin/warmer/SitemapWarmer.php

WarmerCommands.php in src/Commands/WarmerCommands.php