```
sqlalchemy.exc.ArgumentError: Mapper mapped class Game->game could not assemble any primary key columns for mapped table 'game'
```
```
sqlalchemy.exc.NoForeignKeysError: Could not determine join condition between parent/child tables on relationship Mod.game - there are no foreign keys linking these tables.  Ensure that referencing columns are associated with a ForeignKey or ForeignKeyConstraint, or specify a 'primaryjoin' expression.
```
This is how the errors look like, in case you ever encounter them. The first one is pretty self-explanatory, the second one not really.