code: def GetRegistryFileMapping(self, registry_file):
      
      if not registry_file:
        return ''
  
      candidate_mappings = []
      for mapping in self._REGISTRY_FILE_MAPPINGS_NT:
        if not mapping.unique_key_paths:
          continue
  
        # If all unique key paths are found consider the file to match.
        match = True
        for key_path in mapping.unique_key_paths:
          registry_key = registry_file.GetKeyByPath(key_path)
          if not registry_key:
            match = False
  
        if match:
          candidate_mappings.append(mapping)
  
      if not candidate_mappings:
        return ''
  
      if len(candidate_mappings) == 1:
        return candidate_mappings[0].key_path_prefix
  
      key_path_prefixes = frozenset([
          mapping.key_path_prefix for mapping in candidate_mappings])
  
      expected_key_path_prefixes = frozenset([
          'HKEY_CURRENT_USER',
          'HKEY_CURRENT_USER\\Software\\Classes'])
  
      if key_path_prefixes == expected_key_path_prefixes:
        return 'HKEY_CURRENT_USER'
  
      raise RuntimeError('Unable to resolve Windows Registry file mapping.')
docs: Determines the Registry file mapping based on the content of the file.
  
      Args:
        registry_file (WinRegistyFile): Windows Registry file.
  
      Returns:
        str: key path prefix or an empty string.
  
      Raises:
        RuntimeError: if there are multiple matching mappings and
            the correct mapping cannot be resolved.