How to get block hash from a block number

[f-squirrel]

I have noticed that subxt requires providing a block hash to download the block or block header.

How do I get a block hash if I only know its number?

In versions prior 0.34.0 there was the following API:

client.rpc().block_hash(block_id)

Where block_id is a number.

P.S. Unfortunately, I cannot subscribe to block updates. I use it as described here.

[f-squirrel]

I found the following way to do it:

        let legacy_rpc_client = LegacyRpcMethods::<PolkadotConfig>::new(rpc_client.clone());
        legacy_rpc_client.chain_get_block_hash(block_number).await

I have to hold both LegacyRpcMethods and OnlineClient. It might be helpful to be able to get one from another since, anyway, both hold an Arc` to it.