Function advancing_in 

pub(super) fn advancing_in<T: 'static>(
    order: FrameBehaviourOrder,
    tick: impl FnMut(&mut T, &World, &mut Frame) + 'static,
) -> OnFrame

The behaviour that advances the T of the entity it is spawned on, at order.

For an object whose tick reads what another object’s tick writes: the order is what makes the read see this frame’s write, where two ticks in the default band have no order between them.