code: def get_group(self, filename: str) -> Optional[Dict[str, str]]:
      grp_filename = f"__grp__{filename}"
      if not self.has_file(grp_filename):
          return None
      grp_filepath = self._make_path(grp_filename)
      with open(grp_filepath) as f:
          grp_data = json.load(f)
      child_paths = grp_data.get("child_paths", None)
      # Invalid group data.
      if child_paths is None:
          return None
      result = {}
      for c, p in child_paths.items():
          if os.path.exists(p):
              result[c] = p
      return result
  
imports: import json
  import os
  import random
  from abc import ABC, abstractmethod
  from pathlib import Path
  from typing import Dict, Optional
  import hashlib
label_desc: Use image node_id 5 for calling the FileCacheManager obj's underlying member method code with example usage: obj.get_group(filename) and returns: result, None, None