Headers.get typing signature is annoyingly loose

[ItsDrike]

Hey, I'm filing this as a discussion instead of a bug report issue as it seems like that's the preferred workflow here, but this is essentially a bug report. The Headers class inherits from MutableMapping[str, str] which makes sense, however, it overrides get in a pretty unfortunate and type-loose manner, where headers.get("foo") will give you Any instead of str | None. The definition should use a TypeVar.

httpx2/src/httpx2/httpx2/_models.py

Lines 238 to 246 in cbfc0e0

	def get(self, key: str, default: typing.Any = None) -> typing.Any:
	"""
	Return a header value. If multiple occurrences of the header occur
	then concatenate them together with commas.
	"""
	try:
	return self[key]
	except KeyError:
	return default

[Kludex]

PR welcome.

[ItsDrike]

#1121