Function kind_of 

pub(crate) fn kind_of(
    picture: Option<&str>,
    reads: bool,
    frames: u32,
    medium: Option<&'static str>,
) -> Kind

What a file is (decisions 7 to 9), by its first bytes alone: a picture (picture, as sniff tells it), an animated GIF when it holds several frames, refused where Qt here reads no such picture (reads); else a video, a sound, a contact card or a calendar entry (medium, as sniff_medium tells it); else another file, refused.