Type hinting Inconsistency in beam_search.py


In beam_search.pyfile, the process function (in actual classes), have the follwoing signature

    def process(
        input_ids: torch.LongTensor,
        next_scores: torch.FloatTensor,
        next_tokens: torch.LongTensor,
        next_indices: torch.LongTensor,
        pad_token_id: Optional[int] = None,
        eos_token_id: Optional[Union[int, List[int]]] = None,
        beam_indices: Optional[torch.LongTensor] = None,
    ) -> Tuple[torch.Tensor]:

even though it returns UserDict. Any reason why not annotate with Dict, Mapping rather than Tuple?