add missing file

utils.py

@@ -0,0 +1,16 @@
+from transformers import T5Tokenizer, T5EncoderModel
+import torch
+def sequence_mask(lengths, max_len=None):
+    """
+    Creates a boolean mask from sequence lengths.
+    :param lengths: 1d tensor [batch_size]
+    :param max_len: int
+    """
+    batch_size = lengths.numel()
+    max_len = max_len or lengths.max()
+    return (torch.arange(0, max_len, device=lengths.device)
+            .type_as(lengths)
+            .repeat(batch_size, 1)
+            .lt(lengths.unsqueeze(1))
+            .long())
+