feat(model): add torch.nn.functional import

Author: voidful

tfkit/task/seq2seq/model.py

@@ -4,7 +4,7 @@
 from torch import nn
 from torch.nn.functional import softmax
 from transformers import AutoModel
-
+import torch.nn.functional as F
 from tfkit.task.seq2seq import Preprocessor
 from tfkit.utility.loss import NegativeCElLoss, SelfKDLoss
 from tfkit.utility.model import tie_encoder_decoder_weights