Use better type definitions for the array API custom types

Author: asmeurer

numpy/_array_api/_types.py

@@ -14,10 +14,13 @@
 from . import (Array, int8, int16, int32, int64, uint8, uint16, uint32,
                uint64, float32, float64)
 
-Array = ndarray
-Device = TypeVar('device')
-Dtype = Literal[int8, int16, int32, int64, uint8, uint16,
-                uint32, uint64, float32, float64]
-SupportsDLPack = TypeVar('SupportsDLPack')
-SupportsBufferProtocol = TypeVar('SupportsBufferProtocol')
-PyCapsule = TypeVar('PyCapsule')
+# This should really be recursive, but that isn't supported yet. See the
+# similar comment in numpy/typing/_array_like.py
+NestedSequence = Sequence[Sequence[Any]]
+
+Device = Any
+Dtype = Type[Union[[int8, int16, int32, int64, uint8, uint16,
+                   uint32, uint64, float32, float64]]]
+SupportsDLPack = Any
+SupportsBufferProtocol = Any
+PyCapsule = Any