`__str__` and `__repr__` needed for string formatting
https://github.com/adsharma/py2many/issues/73 and https://github.com/adsharma/py2many/issues/74 (and others) are reliant on `__str__` and `__repr__` for custom classes.

e.g. for Rust, `__str__` and `__repr__` would need to become `Display` and `Debug` traits.