This example tests a corner case, consisting of two steps:

1. A first plan1.py runs two steps, of which the first creates the second.
2. A second plan2.py runs two related steps, with the same inner step, but a different outer one.

The difficulty is that the inner step will still be attached to its detached creator.
When it is recreated, it needs to be detached from its creator,
which implies that the creator should be removed.
