def wrap(self, main_phases, name=None):
    """Returns PhaseGroup with additional main phases."""
    new_main = list(self.main)
    if isinstance(main_phases, collections.Iterable):
      new_main.extend(main_phases)
    else:
      new_main.append(main_phases)
    return PhaseGroup(
        setup=self.setup,
        main=new_main,
        teardown=self.teardown,
        name=name)
Returns PhaseGroup with additional main phases.