6 files declare their use of NormalizerBase

BooleanNormalizer.php in core/modules/serialization/tests/modules/test_datatype_boolean_emoji_normalizer/src/Normalizer/BooleanNormalizer.php
NormalizerBase.php in core/modules/jsonapi/src/Normalizer/NormalizerBase.php
NormalizerBase.php in core/modules/hal/src/Normalizer/NormalizerBase.php
NormalizerBaseTest.php in core/modules/serialization/tests/src/Unit/Normalizer/NormalizerBaseTest.php
Contains \Drupal\Tests\serialization\Unit\Normalizer\NormalizerBaseTest.
StringNormalizer.php in core/modules/jsonapi/tests/modules/jsonapi_test_data_type/src/Normalizer/StringNormalizer.php
TraversableObjectNormalizer.php in core/modules/jsonapi/tests/modules/jsonapi_test_data_type/src/Normalizer/TraversableObjectNormalizer.php

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