✨: make HasNamespace

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

Author: nstarman

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, runtime_checkable
+
+@runtime_checkable
+class HasNamespace(Protocol):
+    """Protocol for classes that have an `__array_namespace__` method.
+
+    This is a runtime checkable protocol.
+
+    Example:
+    
+    >>> import array_api_typing as apt
+    >>>
+    >>> class MyArray:
+    ...     def __array_namespace__(self):
+    ...         return "my namespace"
+    >>>
+    >>> x = MyArray()
+    >>> print(isinstance(x, apt.HasNamespace))
+    True
+
+    """
+
+    def __array_namespace__(self) -> object:
+        ...