code: def GetSubkeyByIndex(self, index):
      
      if index < 0 or index >= self._pyregf_key.number_of_sub_keys:
        raise IndexError('Index out of bounds.')
  
      pyregf_key = self._pyregf_key.get_sub_key(index)
      if not pyregf_key:
        return None
  
      key_path = key_paths.JoinKeyPath([self._key_path, pyregf_key.name])
      return REGFWinRegistryKey(pyregf_key, key_path=key_path)
docs: Retrieves a subkey by index.
  
      Args:
        index (int): index of the subkey.
  
      Returns:
        WinRegistryKey: Windows Registry subkey or None if not found.
  
      Raises:
        IndexError: if the index is out of bounds.