Function store_title 

pub fn store_title(
    store: &Store,
    block_id: &str,
    title: &str,
    replace: Replace,
    still_current: impl Fn() -> bool,
) -> Result<bool, String>

Store title as the block’s session title if replace allows it. A value that is not a usable title is never stored. still_current is asked inside the transaction: a request superseded by a newer one must not store its title after the newer one did. Ok(true) when written.