28 files declare their use of ConfigEntityBase

Action.php in core/modules/system/src/Entity/Action.php
Block.php in core/modules/block/src/Entity/Block.php
ConfigEntityBaseUnitTest.php in core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityBaseUnitTest.php
ConfigEntityBaseWithPluginCollections.php in core/tests/Drupal/Tests/Core/Config/Entity/Fixtures/ConfigEntityBaseWithPluginCollections.php
ConfigEntityStorageTest.php in core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityStorageTest.php
ConfigTest.php in core/modules/config/tests/config_test/src/Entity/ConfigTest.php
ConfigurableLanguage.php in core/modules/language/src/Entity/ConfigurableLanguage.php
ContentLanguageSettings.php in core/modules/language/src/Entity/ContentLanguageSettings.php
DateFormat.php in core/lib/Drupal/Core/Datetime/Entity/DateFormat.php
Editor.php in core/modules/editor/src/Entity/Editor.php
EntityDisplayBase.php in core/lib/Drupal/Core/Entity/EntityDisplayBase.php
EntityDisplayModeBase.php in core/lib/Drupal/Core/Entity/EntityDisplayModeBase.php
EntityLinkTest.php in core/tests/Drupal/Tests/Core/Entity/EntityLinkTest.php
EntityViewsDataTest.php in core/modules/views/tests/src/Kernel/Entity/EntityViewsDataTest.php
FieldConfigBase.php in core/lib/Drupal/Core/Field/FieldConfigBase.php
FieldStorageConfig.php in core/modules/field/src/Entity/FieldStorageConfig.php
FilterFormat.php in core/modules/filter/src/Entity/FilterFormat.php
ImageStyle.php in core/modules/image/src/Entity/ImageStyle.php
Menu.php in core/modules/system/src/Entity/Menu.php
ResponsiveImageStyle.php in core/modules/responsive_image/src/Entity/ResponsiveImageStyle.php
RestResourceConfig.php in core/modules/rest/src/Entity/RestResourceConfig.php
Role.php in core/modules/user/src/Entity/Role.php
SearchPage.php in core/modules/search/src/Entity/SearchPage.php
TestConfigType.php in core/modules/system/tests/modules/module_installer_config_test/src/Entity/TestConfigType.php
Tour.php in core/modules/tour/src/Entity/Tour.php
View.php in core/modules/views/src/Entity/View.php
ViewsConfigEntityTest.php in core/modules/views/tests/modules/views_config_entity_test/src/Entity/ViewsConfigEntityTest.php
Workflow.php in core/modules/workflows/src/Entity/Workflow.php

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