Actually, your question has hundreds of correct answers. because it's completely related to your application scope and design. Let's review the definition of "Best Solution" in this case.
The structure of your files needs to be organized enough to avoid confusion, conflicts, and misuse and they Must Be meaningful, useful, maintainable, and reusable.
So make the situation clear for yourself. Do you have any other Classes like DTOs that need to be placed into the model's directory or not? if put different groups of files with different usage and structure in the same directory, they should be clearly separated by some naming conventions like prefix/suffixes.
--UserDB.py // what you are going to use for your ORM
--UserDTO.py // what you are going to return in the response of your API.
In this solution, you might encounter a situation that you need to import one of them somewhere, and then you can import one of them wrongly or if you need both of them, you need to use an alias for them and it makes confusion for the other developers.