Function sc_finality_grandpa::block_import

pub fn block_import<BE, Block: BlockT, Client, SC>(
    client: Arc<Client>, 
    genesis_authorities_provider: &dyn GenesisAuthoritySetProvider<Block>, 
    select_chain: SC
) -> Result<(GrandpaBlockImport<BE, Block, Client, SC>, LinkHalf<Block, Client, SC>), ClientError> where
    SC: SelectChain<Block>,
    BE: Backend<Block> + 'static,
    Client: ClientForGrandpa<Block, BE> + 'static, 

Make block importer and link half necessary to tie the background voter to it.