skip mask conversion if already 4d

src/axolotl/monkeypatch/utils.py

@@ -225,6 +225,9 @@ def mask_2d_to_4d(
     when they attend to each other within that sequence.
     This expansion transforms the mask to lower triangular form to prevent future peeking.
     """
+
+    if len(mask.size()) == 4:
+        return mask
     bsz, src_len = int(mask.size()[0]), int(mask.size()[1])
     tgt_len = tgt_len if tgt_len is not None else src_len