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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 GetRootKey(self):
 """Retrieves the Windows Registry root key. Returns: WinRegistryKey: Windows Registry root key. Raises: RuntimeError: if there are multiple matching mappings and the correct mapping cannot be resolved. """

    root_registry_key = virtual.VirtualWinRegistryKey('')

    for mapped_key in self._MAPPED_KEYS:
      key_path_segments = key_paths.SplitKeyPath(mapped_key)
      if not key_path_segments:
        continue

      registry_key = root_registry_key
      for name in key_path_segments[:-1]:
        sub_registry_key = registry_key.GetSubkeyByName(name)
        if not sub_registry_key:
          sub_registry_key = virtual.VirtualWinRegistryKey(name)
          registry_key.AddSubkey(sub_registry_key)

        registry_key = sub_registry_key

      sub_registry_key = registry_key.GetSubkeyByName(key_path_segments[-1])
      if (not sub_registry_key and
          isinstance(registry_key, virtual.VirtualWinRegistryKey)):
        sub_registry_key = virtual.VirtualWinRegistryKey(
            key_path_segments[-1], registry=self)

        registry_key.AddSubkey(sub_registry_key)

    return root_registry_key