Adds a new activity that goes backwards in the trajectory.
rollback(traj, amount, times = 1, check)the trajectory object.
the amount of activities to roll back (of the same level; it does not go into branches).
the number of repetitions until an arrival may continue.
a callable object (a function) that must return a boolean. If
present, the times parameter is ignored, and the activity uses this
function to check whether the rollback must be done or not.
The trajectory object.
Other methods to deal with trajectories: create_trajectory, get_head, get_tail, get_n_activities, seize, release, set_attribute, timeout, branch.