Expose SharedMemoryArrayMetadata in the public API.

PiperOrigin-RevId: 872892220

Author: iindyk

CHANGELOG.md

@@ -16,6 +16,7 @@ changes. Best viewed [here](https://google-grain.readthedocs.io/en/latest/change
     in background with `start_prefetch` call.
   * Immediately starts processing elements in the background after restoring
     from a checkpoint with Orbax.
+  * Exposes `SharedMemoryArrayMetadata` in a public API as a metadata descriptor for `SharedMemoryArray`.
 
 * Breaking changes:
   * Custom implementations of `RandomAccessDataSource` should accept `int`

docs/grain.multiprocessing.rst

@@ -11,3 +11,6 @@ List of Members
 .. autoclass:: SharedMemoryArray
    :members:
 
+.. autoclass:: SharedMemoryArrayMetadata
+   :members:
+

grain/multiprocessing.py

@@ -15,7 +15,11 @@
 
 
 # pylint: disable=g-importing-member
+# pylint: disable=g-multiple-import
 # pylint: disable=unused-import
 
-from grain._src.python.ipc.shared_memory_array import SharedMemoryArray
+from grain._src.python.ipc.shared_memory_array import (
+    SharedMemoryArray,
+    SharedMemoryArrayMetadata,
+)
 from grain._src.python.options import MultiprocessingOptions