windows-rs type lib coclass interface problem

Question

I would like to ask how to handle the interface in Coclass.The following is the library obtained through oleview.exe. There is an interface in Coclass.

[
  uuid(307230E1-B48F-11D4-B053-00A0D21AFA30),
  helpstring("Cross Krc Service Factory CoClass")
]
coclass KrcServiceFactory {
    [default] interface IKServiceFactory;
};

[
  odl,
  uuid(3E858FB9-2191-4893-8BF2-41E997C0A4BB),
  helpstring("KUKA Service Factory Interface"),
  oleautomation
]
interface IKServiceFactory : IUnknown {
    HRESULT _stdcall GetService(
                    [in] BSTR strServiceID, 
                    [in] BSTR strClientID, 
                    [out, retval] IKService** ppService);
};
[
  odl,
  uuid(3E858FB8-2191-4893-8BF2-41E997C0A4BB),
  helpstring("KUKA Service Interface"),
  oleautomation
]
interface IKService : IUnknown {
};

So how to create this interface definition and use windows-rs instantiate it? Is the code below correct? How to define IKService** ppService?

#[interface("3E858FB9-2191-4893-8BF2-41E997C0A4BB")]
unsafe trait IKServiceFactory: IUnknown {
    fn GetService(&self, service_id: BSTR, client_id:BSTR) -> IKService;
}
#[interface("3E858FB8-2191-4893-8BF2-41E997C0A4BB")]
unsafe trait IKService : IUnknown { 
}