code: def create_arc(self, mace_type, name):
          '''
          Creates the story arc and initial tree for that arc
          for the current outline. Returns the resulting Arc
          instance.
          '''
          arc = Arc(mace_type=mace_type, outline=self, name=name)
          arc.save()
          milestone_count = arc.generate_template_arc_tree()
          if milestone_count == 7:  # pragma: no cover
              arc.refresh_from_db()
              return arc
          else:
              raise ArcIntegrityError('Something went wrong during arc template generation'f create_arc(self, mace_type, name):
          '''
          Creates the story arc and initial tree for that arc
          for the current outline. Returns the resulting Arc
          instance.
          '''
          arc = Arc(mace_type=mace_type, outline=self, name=name)
          arc.save()
          milestone_count = arc.generate_template_arc_tree()
          if milestone_count == 7:  # pragma: no cover
              arc.refresh_from_db()
              return arc
          else:
              raise ArcIntegrityError('Something went wrong during arc template generation')
docs: Creates the story arc and initial tree for that arc
          for the current outline. Returns the resulting Arc
          instance.