sing forward-filtering-and-backward-sampling algorithm.

            - `alpha`: Smoothing parameter for unigram sampling, and dropout probability of merge operations for
              BPE-dropout.

    Attributes:
        sp_model (`SentencePieceProcessor`):
            The *SentencePiece* processor that is used for every conversion (string, tokens and IDs).
        whitespaces (`set`):
            The whitespaces that are replaced in the whitespace normalization in preprocessing.
        non_printing_characters_re (`Pattern`):
            The compiled regular expression to remove non-printing characters in preprocessing.
    FNÚsp_model_kwargsÚ