chore: import upstream snapshot with attribution

decoding/GAD/fairseq/data/roll_dataset.py

@@ -0,0 +1,18 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+#
+# This source code is licensed under the MIT license found in the
+# LICENSE file in the root directory of this source tree.
+
+import torch
+
+from . import BaseWrapperDataset
+
+
+class RollDataset(BaseWrapperDataset):
+    def __init__(self, dataset, shifts):
+        super().__init__(dataset)
+        self.shifts = shifts
+
+    def __getitem__(self, index):
+        item = self.dataset[index]
+        return torch.roll(item, self.shifts)