DOC: default_device can be None

Author: ev-br

src/array_api_stubs/_draft/info.py

@@ -80,7 +80,9 @@ def default_device() -> device:
     Returns
     -------
     out: device
-        an object corresponding to the default device.
+        an object corresponding to the default device or ``None``.
+        A conforming array library may return ``None`` if the default device is not
+        predictable due to library specific device placement rules.
 
     Notes
     -----