class_docstr: Produces inputs and answer spans for Squad.
class_docstr_tok: ["Produces","inputs","and","answer","spans","for","Squad","."]
code: def _lookup_tokens(self, text, source_is_doc=True):
      # This is useful in SquadMetricReporter._unnumberize()
      return (
          self.doc_tensorizer._lookup_tokens(text)
          if source_is_doc
          else self.ques_tensorizer._lookup_tokens(text)
      )
  
imports: from typing import List
  import torch
  from pytext.common.constants import SpecialTokens
  from pytext.config.component import ComponentType, create_component
  from pytext.data.tensorizers import TokenTensorizer
  from pytext.data.tokenizers import Tokenizer, WordPieceTokenizer
  from pytext.data.utils import pad_and_tensorize, VocabBuilder, Vocabulary
label_desc: Use image node_id 4 for calling the SquadTensorizer obj's underlying member method code with example usage: obj._lookup_tokens(text, source_is_doc) and returns: unknown