/usr/share/php/Symfony/Component/Form/Extension/Core/DataTransformer/ is in php-symfony-form 2.3.21+dfsg-4+deb8u3.
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/usr/share/php/Symfony/Component/Form/Extension/Core/DataTransformer/ArrayToPartsTransformer.php
/usr/share/php/Symfony/Component/Form/Extension/Core/DataTransformer/BaseDateTimeTransformer.php
/usr/share/php/Symfony/Component/Form/Extension/Core/DataTransformer/BooleanToStringTransformer.php
/usr/share/php/Symfony/Component/Form/Extension/Core/DataTransformer/ChoiceToBooleanArrayTransformer.php
/usr/share/php/Symfony/Component/Form/Extension/Core/DataTransformer/ChoiceToValueTransformer.php
/usr/share/php/Symfony/Component/Form/Extension/Core/DataTransformer/ChoicesToBooleanArrayTransformer.php
/usr/share/php/Symfony/Component/Form/Extension/Core/DataTransformer/ChoicesToValuesTransformer.php
/usr/share/php/Symfony/Component/Form/Extension/Core/DataTransformer/DataTransformerChain.php
/usr/share/php/Symfony/Component/Form/Extension/Core/DataTransformer/DateTimeToArrayTransformer.php
/usr/share/php/Symfony/Component/Form/Extension/Core/DataTransformer/DateTimeToLocalizedStringTransformer.php
/usr/share/php/Symfony/Component/Form/Extension/Core/DataTransformer/DateTimeToRfc3339Transformer.php
/usr/share/php/Symfony/Component/Form/Extension/Core/DataTransformer/DateTimeToStringTransformer.php
/usr/share/php/Symfony/Component/Form/Extension/Core/DataTransformer/DateTimeToTimestampTransformer.php
/usr/share/php/Symfony/Component/Form/Extension/Core/DataTransformer/IntegerToLocalizedStringTransformer.php
/usr/share/php/Symfony/Component/Form/Extension/Core/DataTransformer/MoneyToLocalizedStringTransformer.php
/usr/share/php/Symfony/Component/Form/Extension/Core/DataTransformer/NumberToLocalizedStringTransformer.php
/usr/share/php/Symfony/Component/Form/Extension/Core/DataTransformer/PercentToLocalizedStringTransformer.php
/usr/share/php/Symfony/Component/Form/Extension/Core/DataTransformer/ValueToDuplicatesTransformer.php