✨: make HasNamespace

Signed-off-by: Nathaniel Starkman <nstarman@users.noreply.github.com>

Author: nstarman

.gitignore

@@ -22,3 +22,6 @@ venv/
 
 # Build docs
 /src/array_api_typing/_version.py
+
+# Mac files
+.DS_Store

src/array_api_typing/__init__.py

@@ -1,5 +1,6 @@
 """Static typing support for the array API standard."""
 
-__all__ = ()
+__all__ = ["HasNamespace"]
 
 from ._version import version as __version__ , version_tuple as __version_tuple__
+from ._namespace import HasNamespace

src/array_api_typing/_namespace.py

@@ -0,0 +1,28 @@
+"""Static typing support for the array API standard."""
+
+__all__ = ["HasNamespace"]
+
+from typing import Protocol
+
+
+class HasNamespace(Protocol):
+    """Protocol for classes that have an `__array_namespace__` method.
+
+    This is for type-annotating objects that should
+
+    Example:
+    >>> import array_api_typing as xpt
+    >>>
+    >>> class MyArray:
+    ...     def __array_namespace__(self):
+    ...         return object()
+    >>>
+    >>> x = MyArray()
+    >>> def has_namespace(x: xpt.HasNamespace) -> bool:
+    ...     return hasattr(x, "__array_namespace__")
+    >>> has_namespace(x)
+    True
+
+    """
+
+    def __array_namespace__(self) -> object: ...  # noqa: PLW3201