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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _GetFileByPath(self, key_path_upper):
 """Retrieves a Windows Registry file for a specific path. Args: key_path_upper (str):
 Windows Registry key path, in upper case with a resolved root key alias. Returns: tuple: consists: str: upper case key path prefix WinRegistryFile: corresponding Windows Registry file or None if not available. """

    # TODO: handle HKEY_USERS in both 9X and NT.

    key_path_prefix, registry_file = self._GetCachedFileByPath(key_path_upper)
    if not registry_file:
      for mapping in self._GetFileMappingsByPath(key_path_upper):
        try:
          registry_file = self._OpenFile(mapping.windows_path)
        except IOError:
          registry_file = None

        if not registry_file:
          continue

        if not key_path_prefix:
          key_path_prefix = mapping.key_path_prefix

        self.MapFile(key_path_prefix, registry_file)
        key_path_prefix = key_path_prefix.upper()
        break

    return key_path_prefix, registry_file