pub(super) fn fee<State, Ver>(
api_ver: Version,
) -> Result<Api<State, Error, Ver>>where
State: 'static + Send + Sync + ReadState,
Ver: 'static + StaticVersionType,
<State as ReadState>::State: Send + Sync + MerklizedStateDataSource<SeqTypes, FeeMerkleTree, { FeeMerkleTree::ARITY }> + MerklizedStateHeightPersistence,