make multipack sampler patch explicit (#3096)

* make multipack sampler patch explicit

* combining

tests/test_packed_batch_sampler.py

@@ -48,7 +48,13 @@ class TestBatchedSamplerPacking:
         max_seq_length,
         sequential,
     ):
-        import axolotl.monkeypatch.data.batch_dataset_fetcher  # pylint: disable=unused-import  # noqa: F401
+        from axolotl.monkeypatch.data.batch_dataset_fetcher import (
+            apply_multipack_dataloader_patch,
+            remove_multipack_dataloader_patch,
+        )
+
+        # Apply the patch for multipack handling
+        apply_multipack_dataloader_patch()
 
         dataset = dataset_winglian_tiny_shakespeare["train"]
 
@@ -101,10 +107,14 @@ class TestBatchedSamplerPacking:
             for pack in batch:
                 batch_idxs.extend(pack)
 
-        for batch in loader:
-            assert batch["input_ids"].numel() <= batch_size * max_seq_length
-            assert batch["input_ids"].shape[1] == max_seq_length
+        try:
+            for batch in loader:
+                assert batch["input_ids"].numel() <= batch_size * max_seq_length
+                assert batch["input_ids"].shape[1] == max_seq_length
 
-        original_idxs = set(range(len(train_dataset)))
-        assert original_idxs == set(batch_idxs)
-        assert len(batch_idxs) == len(set(batch_idxs))
+            original_idxs = set(range(len(train_dataset)))
+            assert original_idxs == set(batch_idxs)
+            assert len(batch_idxs) == len(set(batch_idxs))
+        finally:
+            # Clean up: remove the patch after the test
+            remove_multipack_dataloader_patch()