Function move_group

fn move_group(
    a: &mut Animated,
    orig: &[Keyframe],
    sel: &[usize],
    dt: f64,
    dv: f64,
) -> Vec<usize>

Re-lay orig with the keys at sel shifted by (dt, dv) and write it back; returns their new indices. A moved key landing on an unmoved one replaces it, exactly like Animated::move_key.