code: def __init__(self, num_classes):
      self.pq_per_cat = defaultdict(PQStatCat)
      self.num_classes = num_classes
  
file_path: PaddleSeg/contrib/PanopticDeepLab/utils/evaluation/panoptic.py
imports: from collections import defaultdict, OrderedDict
  import numpy
label_desc: Use image node_id 1 to create a new PQStat object  with example: obj = PQStat(num_classes)