6 files declare their use of TransactionManagerInterface

Connection.php in core/modules/pgsql/src/Driver/Database/pgsql/Connection.php
Connection.php in core/modules/mysqli/src/Driver/Database/mysqli/Connection.php
Connection.php in core/lib/Drupal/Core/Database/Connection.php
Connection.php in core/modules/sqlite/src/Driver/Database/sqlite/Connection.php
Connection.php in core/modules/mysql/src/Driver/Database/mysql/Connection.php
StubConnection.php in core/tests/Drupal/Tests/Core/Database/Stub/StubConnection.php

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