code: def _get_tokens(self, s):
      if not s:
          return []
      return self._normalize_answer(s).split()
  
imports: import re
  import string
  from collections import Counter
  from itertools import zip_longest
  from typing import Dict, List
  import numpy
  from pytext.common.constants import Stage
  from pytext.metric_reporters.channel import Channel, ConsoleChannel, FileChannel
  from pytext.metric_reporters.metric_reporter import MetricReporter
  from pytext.metrics import compute_classification_metrics, LabelPrediction
  from pytext.metrics.squad_metrics import SquadMetrics
label_desc: Use image node_id 17 for calling the SquadMetricReporter obj's underlying member method code with example usage: obj._get_tokens(s) and returns: self, list