fn get_header<'a>(
&'a self, header_hash: &'a BlockHash, height_hint: Option<u32>,
) -> AsyncBlockSourceResult<'a, BlockHeaderData> {
fn get_header<'a>(
&'a self, header_hash: &'a BlockHash, height_hint: Option<u32>,
) -> AsyncBlockSourceResult<'a, BlockHeaderData> {