code: def _sent_to_token_features(self, sent):
      sent_features = []
      for tok in sent:
          if self.validate_token(tok):
              sent_features.append(
                  [
                      tok.idx,
                      tok.idx + len(tok),
                      self.text_from_token(tok),
                  ]
              )
      return sent_features
  
imports: from typing import List, Tuple, Union, Optional, Callable, Dict
  from collections import deque
  from scattertext.features.FeatsFromSpacyDoc import FeatsFromSpacyDoc
  from scattertext.features.featoffsets.feat_and_offset_getter import FeatAndOffsetGetter
  from scattertext.Common import MY_ENGLISH_STOP_WORDS
label_desc: Use image node_id 4 for calling the FlexibleNGramFeaturesBase obj's underlying member method code with example usage: obj._sent_to_token_features(sent) and returns: sent_features