code: def __iadd__(self, pq_stat_cat):
      self.iou += pq_stat_cat.iou
      self.tp += pq_stat_cat.tp
      self.fp += pq_stat_cat.fp
      self.fn += pq_stat_cat.fn
      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 2 for calling the PQStatCat obj's underlying member method code with example usage: obj.__iadd__(pq_stat_cat) and returns: self