pub(super) fn state_signature<N, S, ApiVer: StaticVersionType + 'static>(
_: ApiVer,
api_ver: Version,
) -> Result<Api<S, Error, ApiVer>>where
N: ConnectedNetwork<PubKey>,
S: 'static + Send + Sync + ReadState,
S::State: Send + Sync + StateSignatureDataSource<N>,