code: def _GetUsers(self, key_path_suffix):
      
      user_key_name, _, key_path_suffix = key_path_suffix.partition(
          definitions.KEY_PATH_SEPARATOR)
  
      # HKEY_USERS\.DEFAULT is an alias for HKEY_USERS\S-1-5-18 which is
      # the Local System account.
      if user_key_name == '.DEFAULT':
        search_key_name = 'S-1-5-18'
      else:
        search_key_name = user_key_name
  
      user_profile_list_key = self.GetKeyByPath(self._USER_PROFILE_LIST_KEY_PATH)
      if not user_profile_list_key:
        return None
  
      for user_profile_key in user_profile_list_key.GetSubkeys():
        if search_key_name == user_profile_key.name:
          profile_path_value = user_profile_key.GetValueByName('ProfileImagePath')
          if not profile_path_value:
            break
  
          profile_path = profile_path_value.GetDataAsObject()
          if not profile_path:
            break
  
          key_name_upper = user_profile_key.name.upper()
          if key_name_upper.endswith('_CLASSES'):
            profile_path = '\\'.join([
                profile_path, 'AppData', 'Local', 'Microsoft', 'Windows',
                'UsrClass.dat'])
          else:
            profile_path = '\\'.join([profile_path, 'NTUSER.DAT'])
  
          profile_path_upper = profile_path.upper()
          registry_file = self._GetCachedUserFileByPath(profile_path_upper)
          if not registry_file:
            break
  
          key_path_prefix = definitions.KEY_PATH_SEPARATOR.join([
              'HKEY_USERS', user_key_name])
          key_path = ''.join([key_path_prefix, key_path_suffix])
  
          registry_file.SetKeyPathPrefix(key_path_prefix)
          return registry_file.GetKeyByPath(key_path)
  
      return None
docs: Virtual key callback to determine the users sub keys.
  
      Args:
        key_path_suffix (str): users Windows Registry key path suffix with
            leading path separator.
  
      Returns:
        WinRegistryKey: the users Windows Registry key or None if not available.