code: def PruneNgram(self, hist, word):
      counts_for_hist = self.counts[len(hist)][hist]
      assert (
          word != self.backoff_symbol
          and word in counts_for_hist.word_to_count
      )
      count = counts_for_hist.word_to_count[word]
      del counts_for_hist.word_to_count[word]
      counts_for_hist.word_to_count[self.backoff_symbol] += count
      # the next call adds the count to the symbol 'word' in the backoff
      # history-state, and also updates its 'total_count'.
      self.counts[len(hist) - 1][hist[1:]].AddCount(word, count)
  
imports: import argparse
  import math
  import sys
  from collections import defaultdict
label_desc: Use image node_id 13 for calling the NgramCounts obj's underlying member method code with example usage: obj.PruneNgram(hist, word) without return types