Why force tokens in Bart decoding
https://github.com/huggingface/transformers/blob/master/src/transformers/modeling_bart.py#L955

What's the meaning of this line? Why decode \<S\>  when cur_len = 1? Why not when cur_len = 0?
see https://github.com/huggingface/transformers/issues/3668<|||||>> see #3668

thanks a lot!