This is an other thing. The `DocumentManager` does it and did it before. I would say :-1:, but i can't do that refactoring in that PR. I spoke with @dbu and we think we should put all session request of `DocumentManager`/`UnitOfWork` into persisters as the ORM does. This will bring much more readable code and most important: we will be able to test both by just mocking that persisters. Mocking the session atm would mean to mock on of the implementations, what is not right, and is the reason for the low code-coverage of test for both classes, right?