Fix incorrect type hint in experimental engine

[thomasaarholt]

This type hint was causing our Python 3.9 test suit to throw some type errors.

    def generate(self, content, system_prompt: Union[str | List[Union[str, bytes]]] = None, **kwargs):
E   TypeError: unsupported operand type(s) for |: 'type' and '_GenericAlias'

The typehint wasn't correct on any Python version, but Python 3.9 doesn't support | between types. The new hint is more correct, at least. Not sure why it can take a list[bytes] though.

[fralik]

2 cents:
| syntax requires python >= 3.10, since textgrad is python >= 3.9 (

textgrad/setup.py

Line 13 in 6ede5fb

python_requires=">=3.9",

), then it's probably better to use , syntax.

[thomasaarholt]

Ugh, I see my editor auto formatted it! Let me fix.

[thomasaarholt]

@fralik, yep, that was what my edit did, but then my editor added tons of formatting noise. Fixed now.

That was the only case of | used for type hinting in the codebase, according to my grep.

[vinid]

Thank you!