Function complete 

pub fn complete(
    word: &str,
    aliases: &HashMap<String, String>,
    query_command: Option<&str>,
    sort: Option<&str>,
) -> Vec<String>

Completion candidates for a partial address: expansions of every alias whose nick starts with word (case-insensitive), then query_command results, sorted and deduplicated. sort is mutt’s $sort_alias: “address” (by the expansion; the default), “alias” (by nick; “unsorted” reads the same, the file being a map), with “reverse-” flipping either.