code: def __iadd__(self, pq_stat):
      for label, pq_stat_cat in pq_stat.pq_per_cat.items():
          self.pq_per_cat[label] += pq_stat_cat
      return self
  
imports: from collections import defaultdict
  import numpy
  from paddlepanseg.cvlibs import build_info_dict
  from paddlepanseg.utils import decode_pan_id
  from .evaluator import Evaluator
label_desc: Use image node_id 3 for calling the PQStat obj's underlying member method code with example usage: obj.__iadd__(pq_stat) and returns: self