Function import_step 

fn import_step(
    here: &str,
    seal: &Seal,
    vault: &(PathBuf, [u8; 32]),
    region: Option<&Region>,
    now: i64,
) -> bool

One step of the import, the first and every one after: the texts after the reader’s marks, BATCH at most (the plain texts first, then the multimedia ones), their media within MEDIA_BATCH bytes, written to this phone’s log. A multimedia message whose media do not fit waits, with every one after it, for the next step. Whether anything was written.