mixer.Select doesn't select already exists User from the DB

Following the documentation [mixer.SELECT](https://mixer.readthedocs.io/en/latest/api.html#select-a-relation-from-database) will choose from an already exists instance of a model. But I'm having an error. mixer.SELECT create users instead of selecting users in the DB.


Start with the mixer.SELECT API documentation and the database-selection path it describes; the issue provides no source file or test to target. Reproduce the reported case and consider the work done when an existing User is selected instead of a new User being created.

Written by the indexing model from the issue text.