class_docstr: Object required by Translator.translate().
  If not None, `pass_through_dict` is an arbitrary dictionary instantiated from a JSON object
  via `make_input_from_dict()`, and it contains extra fields found in an input JSON object.
  If `--output-type json` is selected, all such fields that are not fields used or changed by
  Sockeye will be included in the output JSON object. This provides a mechanism for passing
  fields through the call to Sockeye.
class_docstr_tok: ["Object","required","by","Translator.translate","(",")",".","If","not","None",",","`","pass_through_dict","`","is","an","arbitrary","dictionary","instantiated","from","a","JSON","object","via","`","make_input_from_dict","(",")","`",",","and","it","contains","extra","fields","found","in","an","input","JSON","object",".","If","`","--","output-type","json","`","is","selected",",","all","such","fields","that","are","not","fields","used","or","changed","by","Sockeye","will","be","included","in","the","output","JSON","object",".","This","provides","a","mechanism","for","passing","fields","through","the","call","to","Sockeye","."]
docstr: Returns the target prefix tokens of this instance.
docstr_tok: ["Returns","the","target","prefix","tokens","of","this","instance","."]
code: def get_target_prefix_tokens(self) -> Tokens:
      """
      Returns the target prefix tokens of this instance.
      """
      return (
          self.target_prefix_tokens
          if self.target_prefix_tokens is not None
          else []
      )
  
imports: import copy
  import itertools
  import json
  import logging
  from dataclasses import dataclass
  from functools import partial
  from typing import Any, Callable, Dict, Generator, List, Optional, Set, Tuple, Union
  import numpy
  import torch
  from .None import constants
  from .None import lexicon
  from .None import utils
  from .None import vocab
  from .beam_search import CandidateScorer, get_search_algorithm, GreedySearch, SearchResult
  from .data_io import tokens2ids, get_prepended_token_length
  from .model import SockeyeModel
label_desc: Use image node_id 6 for calling the TranslatorInput obj's underlying member method code with example usage: obj.get_target_prefix_tokens() and returns: unknown