TypeError on import: "USBDevice" | None union syntax fails with forward reference strings

[rlinus]

usbipd fails to import on Python 3.11 with the following traceback:

Traceback (most recent call last):
File "/opt/homebrew/anaconda3/envs/usbipd/bin/usbipd", line 3, in
from usbipd import main
File ".../site-packages/usbipd.py", line 12, in
from usb_device import USBDevice, USBDeviceManager
File ".../site-packages/usb_device.py", line 344, in
class USBDeviceManager:
File ".../site-packages/usb_device.py", line 364, in USBDeviceManager
def find_by_bus_id(self, bus_id: str) -> "USBDevice" | None:
TypeError: unsupported operand type(s) for |: 'str' and 'NoneType'

Cause:

In usb_device.py, several methods use the X | None union syntax with a forward
reference string:

def find_by_bus_id(self, bus_id: str) -> "USBDevice" | None: # line 366
def find_by_vid_pid(...) -> "USBDevice" | None: # line 403
def find_by_binding(...) -> "USBDevice" | None: # line 433

The | union operator (PEP 604) works on actual type objects at runtime, but
"USBDevice" is a string (forward reference), and str.or is not defined.
This causes a TypeError at class body evaluation time.

Fix:

Add from future import annotations at the top of usb_device.py. This makes
all annotations lazily evaluated as strings, so the | operator is never
actually called at runtime.

Alternatively, replace "USBDevice" | None with Optional["USBDevice"] from
typing.

Environment:

• usbipd 0.0.7
• Python 3.11.15
• macOS (Apple Silicon)