Function ratchet_to_checkpoint_with_config 

pub async fn ratchet_to_checkpoint_with_config(
    fullnode: &mut Client,
    archive: Option<&mut Client>,
    cache: &mut EpochCache,
    target_seq: u64,
    config: &RatchetConfig,
) -> Result<(), LightClientError>

Available on crate feature unstable only.

Advance cache forward so that it covers target_seq.

If archive is provided the ratchet uses it for historical reads and falls back to fullnode on archive misses or errors. On return, the cache holds the committee for the epoch that contains target_seq (subject to the server returning truthful epoch boundaries; the cache independently BLS-verifies each end-of-epoch summary it accepts).