5 files declare their use of ConfigFormBaseTrait

ConfigFormBaseTraitTest.php in core/tests/Drupal/Tests/Core/Form/ConfigFormBaseTraitTest.php
ContactFormEditForm.php in core/modules/contact/src/ContactFormEditForm.php
CronForm.php in core/modules/system/src/Form/CronForm.php
NegotiationBrowserDeleteForm.php in core/modules/language/src/Form/NegotiationBrowserDeleteForm.php
SearchPageListBuilder.php in core/modules/search/src/SearchPageListBuilder.php

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