This allows the degree of VTFM optimization to be adjusted. This is usually one of the schedules from the autosched module (autosched.slow, autosched.normal, autosched.fast, autosched.very_fast, or autosched.fastest) or you can provide your own schedule object (see Section 6.12). See the modlib/modeller/automodel/autosched.py file for more information.
See Section 2.2.2 for an example.