code: def log(self, extras=None):
      d = self.get(extras)
      strs = []
      for k, v in d.items():
          strs.append("{}: {}".format(k, str(v)))
      return self.delimiter.join(strs)
  
file_path: PaddleDetection/ppdet/utils/stats.py
imports: import collections
  import numpy
label_desc: Use image node_id 4 for calling the TrainingStats obj's underlying member method code with example usage: obj.log(extras) and returns: self