Function define_api 

pub(super) fn define_api<S, ApiVer: StaticVersionType + 'static>(
    opt: Options,
    api_ver: Version,
) -> Result<Api<S, Error, ApiVer>>
where
    S: ReadState + Send + Sync + 'static,
    S::State: AvailabilityDataSource<SeqTypes> + MerklizedStateDataSource<SeqTypes, BlockMerkleTree, { BlockMerkleTree::ARITY }> + NodeStateDataSource + StakeTableDataSource<SeqTypes> + VersionedDataSource,
    for<'a> <S::State as VersionedDataSource>::ReadOnly<'a>: NodeStorage<SeqTypes>,