Function fetch_included_from_relay_chain 

pub async fn fetch_included_from_relay_chain<B: BlockT>(
    relay_client: &impl RelayChainInterface,
    backend: &impl Backend<B>,
    at: Hash,
    para_id: ParaId,
) -> Result<Option<(B::Header, B::Hash)>, RelayChainError>

Fetch the included block from the relay chain.