A questions about decoder in seq2seq-torch

https://github.com/graykode/nlp-tutorial/blob/6e171b914ed28eb04dc9176916a99e9a996a7951/4-1.Seq2Seq/Seq2Seq-Torch.py#L92
Hi,I‘m a nlp rookie.I want to ask you a question.I read the seq2seq's paper,which use t-1 output as the t input in decoder. Your code in this line use 'SPPPPP' as the decoder input.So,is this way harm to the result?
If you see this issues, please answer me in your free time.
Although my english is poor, I still want to express my gratitude to you.