6 files declare their use of PluginExample

DefaultPluginManagerTest.php in core/tests/Drupal/KernelTests/Core/Plugin/DefaultPluginManagerTest.php
Example3.php in core/modules/system/tests/modules/plugin_test/src/Plugin/plugin_test/custom_annotation/Example3.php
Example4.php in core/modules/system/tests/modules/plugin_test/src/Plugin/plugin_test/custom_annotation/Example4.php
Example5.php in core/modules/system/tests/modules/plugin_test/src/Plugin/plugin_test/custom_annotation/Example5.php
ExampleWithAttributeAndAnnotation.php in core/modules/system/tests/modules/plugin_test/src/Plugin/plugin_test/custom_annotation/ExampleWithAttributeAndAnnotation.php
ExampleWithOtherModuleDependency.php in core/modules/system/tests/modules/plugin_test/src/Plugin/plugin_test/custom_annotation/ExampleWithOtherModuleDependency.php

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