Function fetch_block_range 

pub(super) fn fetch_block_range<Types, S, P>(
    fetcher: Arc<Fetcher<Types, S, P>>,
    start: u64,
    end: u64,
)
where
    Types: NodeType,
    Header<Types>: QueryableHeader<Types>,
    Payload<Types>: QueryablePayload<Types>,
    S: VersionedDataSource + 'static,
    for<'a> S::Transaction<'a>: UpdateAvailabilityStorage<Types>,
    P: AvailabilityProvider<Types>,