7 methods override ComplexDataNormalizer::normalize() in Drupal 9

BooleanItemNormalizer::normalize in core/modules/serialization/tests/modules/test_fieldtype_boolean_emoji_normalizer/src/Normalizer/BooleanItemNormalizer.php

ConfigEntityNormalizer::normalize in core/modules/serialization/src/Normalizer/ConfigEntityNormalizer.php

ContentEntityNormalizer::normalize in core/modules/serialization/src/Normalizer/ContentEntityNormalizer.php

EntityReferenceFieldItemNormalizer::normalize in core/modules/serialization/src/Normalizer/EntityReferenceFieldItemNormalizer.php

StringNormalizer::normalize in core/modules/jsonapi/tests/modules/jsonapi_test_field_type/src/Normalizer/StringNormalizer.php

TextItemSillyNormalizer::normalize in core/modules/serialization/tests/modules/field_normalization_test/src/Normalization/TextItemSillyNormalizer.php

TimestampItemNormalizer::normalize in core/modules/serialization/src/Normalizer/TimestampItemNormalizer.php