code: def GetNumNgrams(self, hist_len=None):
      ans = 0
      if hist_len is None:
          for hist_len in range(args.ngram_order):
              # note: hist_len + 1 is the actual order.
              ans += self.GetNumNgrams(hist_len)
          return ans
      else:
          for counts_for_hist in self.counts[hist_len].values():
              ans += len(counts_for_hist.word_to_count)
              if self.backoff_symbol in counts_for_hist.word_to_count:
                  ans -= 1  # don't count the backoff symbol, it doesn't produce
                  # its own n-gram line.
          return ans
  
imports: import argparse
  import math
  import sys
  from collections import defaultdict
label_desc: Use image node_id 19 for calling the NgramCounts obj's underlying member method code with example usage: obj.GetNumNgrams(hist_len) and returns: ans, ans