Sequence 內部流程

從User Guide剪出

a) Call start_item() to create the item via the factory.
b) Optionally call pre_do() or some other functionality.
c) Optionally randomize item.
d) Optionally call mid_do() or some other functionality, if desired.
e) Call finish_item().
f) Optionally call post_do() or some other functionality.
g) Optionally call get_response().