Function sc_client::light::blockchain::future_header

pub fn future_header<Block: BlockT, F: Fetcher<Block>>(
    blockchain: &dyn RemoteBlockchain<Block>, 
    fetcher: &F, 
    id: BlockId<Block>
) -> impl Future<Output = Result<Option<Block::Header>, ClientError>>

Returns future that resolves header either locally, or remotely.