class_docstr: A class containing all of the functions supporting generation, to be used as a mixin in
  :class:`~transformers.PreTrainedModel`.
class_docstr_tok: ["A","class","containing","all","of","the","functions","supporting","generation",",","to","be","used","as","a","mixin","in",":","class",":","`","~transformers.PreTrainedModel","`","."]
code: def _prepare_decoder_input_ids_for_generation(
      self,
      input_ids: "torch.LongTensor",
      decoder_start_token_id: int = None,
      bos_token_id: int = None,
  ) -> "torch.LongTensor":
      decoder_start_token_id = self._get_decoder_start_token_id(
          decoder_start_token_id, bos_token_id
      )
      decoder_input_ids = (
          torch.ones(
              (input_ids.shape[0], 1),
              dtype=torch.long,
              device=input_ids.device,
          )
          * decoder_start_token_id
      )
      return decoder_input_ids
  
imports: from dataclasses import dataclass
  from typing import Any, Callable, Dict, Iterable, List, Optional, Tuple, Union
  from .file_utils import ModelOutput
  from .generation_beam_search import BeamScorer, BeamSearchScorer
  from .generation_logits_process import EncoderNoRepeatNGramLogitsProcessor, ForcedBOSTokenLogitsProcessor, ForcedEOSTokenLogitsProcessor, HammingDiversityLogitsProcessor, InfNanRemoveLogitsProcessor, LogitsProcessorList, MinLengthLogitsProcessor, NoBadWordsLogitsProcessor, NoRepeatNGramLogitsProcessor, PrefixConstrainedLogitsProcessor, RepetitionPenaltyLogitsProcessor, TemperatureLogitsWarper, TopKLogitsWarper, TopPLogitsWarper
  from .generation_stopping_criteria import MaxLengthCriteria, MaxNewTokensCriteria, MaxTimeCriteria, StoppingCriteriaList, validate_stopping_criteria
  from fastNLP.envs.imports import _NEED_IMPORT_TORCH
  from fastNLP.core.log import logger
label_desc: Use image node_id 6 for calling the GenerationMixin obj's underlying member method code with example usage: obj._prepare_decoder_input_ids_for_generation(input_ids, decoder_start_token_id, bos_token_id) and returns: decoder_input_ids