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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 GetServiceDll(self, key):
 """Get the Service DLL for a service, if it exists. Checks for a ServiceDLL for in the Parameters subkey of a service key in the Registry. Args: key (dfwinreg.WinRegistryKey):
 a Windows Registry key. Returns: str: path of the service DLL or None. """

    parameters_key = key.GetSubkeyByName('Parameters')
    if not parameters_key:
      return None

    service_dll = parameters_key.GetValueByName('ServiceDll')
    if not service_dll:
      return None

    return service_dll.GetDataAsObject()