18 files declare their use of ConfigImporter

ConfigImporterBatch.php in core/lib/Drupal/Core/Config/Importer/ConfigImporterBatch.php
ConfigImporterFieldPurger.php in core/modules/field/src/ConfigImporterFieldPurger.php
ConfigImporterMissingContentTest.php in core/tests/Drupal/KernelTests/Core/Config/ConfigImporterMissingContentTest.php
ConfigImporterTest.php in core/tests/Drupal/KernelTests/Core/Config/ConfigImporterTest.php
ConfigImportRecreateTest.php in core/tests/Drupal/KernelTests/Core/Config/ConfigImportRecreateTest.php
ConfigImportRenameValidationTest.php in core/tests/Drupal/KernelTests/Core/Config/ConfigImportRenameValidationTest.php
ConfigImportSubscriber.php in core/lib/Drupal/Core/EventSubscriber/ConfigImportSubscriber.php
ConfigSingleImportForm.php in core/modules/config/src/Form/ConfigSingleImportForm.php
ConfigSync.php in core/modules/config/src/Form/ConfigSync.php
ConfigTestTrait.php in core/tests/Drupal/Tests/ConfigTestTrait.php
ConfigUninstallViaCliImportTest.php in core/modules/config/tests/src/Kernel/ConfigUninstallViaCliImportTest.php
config_import_test.module in core/modules/config/tests/config_import_test/config_import_test.module
Provides configuration import test helpers.
ContentEntityNullStorageTest.php in core/tests/Drupal/KernelTests/Core/Entity/ContentEntityNullStorageTest.php
ContentTranslationConfigImportTest.php in core/modules/content_translation/tests/src/Kernel/ContentTranslationConfigImportTest.php
field.module in core/modules/field/field.module
Attach custom data fields to Drupal entities.
ImportStorageTransformerTest.php in core/tests/Drupal/KernelTests/Core/Config/ImportStorageTransformerTest.php
install.core.inc in core/includes/install.core.inc
API functions for installing Drupal.
OverriddenConfigImportTest.php in core/modules/language/tests/src/Kernel/OverriddenConfigImportTest.php

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