code: def get_metric(self):
      p = self.pred_real_word / self.pred_word
      r = self.pred_real_word / self.all_word
      return {"f": 2 * (p * r) / (p + r), "pre": p, "rec": r}
  
file_path: textflint/textflint/input/model/metrics/nerspanmetric.py
imports: from abc import ABC
label_desc: Use image node_id 2 for calling the NERSpanMetric obj's underlying member method code with example usage: obj.get_metric() and returns: dict