Update DLPack content to address unsupported use cases

spec/draft/design_topics/data_interchange.rst

@@ -99,4 +99,7 @@ include:
 
 There may be other reasons why it is not possible or desirable for an
 implementation to materialize the array as strided data in memory. In such
-cases, the implementation may raise a `BufferError` in the `__dlpack__` method.
+cases, the implementation may raise a `BufferError` in the `__dlpack__` or
+`__dlpack_device__` method. In case an implementation is never able to export
+its array data via DLPack, it may omit `__dlpack__` and `__dlpack_device__`
+completely, and hence `from_dlpack` may raise an `AttributeError`.

src/array_api_stubs/_draft/creation_functions.py

@@ -236,11 +236,16 @@ def from_dlpack(x: object, /) -> array:
     Raises
     ------
     BufferError
-        The ``__dlpack__`` method on the input array may raise ``BufferError``
-        when the data cannot be exported as DLPack (e.g., incompatible dtype or
-        strides). It may also raise other errors when export fails for other
-        reasons (e.g., not enough memory available to materialize the data).
-        ``from_dlpack`` must propagate such exceptions.
+        The ``__dlpack__`` and ``__dlpack_device__`` methods on the input array
+        may raise ``BufferError`` when the data cannot be exported as DLPack
+        (e.g., incompatible dtype or strides). It may also raise other errors
+        when export fails for other reasons (e.g., not enough memory available
+        to materialize the data). ``from_dlpack`` must propagate such
+        exceptions.
+    AttributeError
+        If the ``__dlpack__`` and ``__dlpack_device__`` methods are not present
+        on the input array. This may happen for libraries that are never able
+        to export their data with DLPack.
     """