code: def _flatten(d):
      if not d:
          return defaultdict(lambda: None)
  
      if isinstance(d, dict):
          return defaultdict(lambda: None, flatten(d))
  
      return defaultdict(lambda: "unable to parse")
  
file_path: dvc/dvc/utils/diff.py
imports: import json
  from collections import defaultdict
  from typing import Dict
  from .flatten import flatten
label_desc: Use image node_id 3 for calling a global function with example usage: _flatten(d) and returns: defaultdict, defaultdict, defaultdict