code: def next_state(self, index, event_time, population_view):
          
          return _next_state(index, event_time, self.transition_set, population_view)
docs: Moves a population between different states using information this state's `transition_set`.
  
          Parameters
          ----------
          index : iterable of ints
              An iterable of integer labels for the simulants.
          event_time : pandas.Timestamp
              When this transition is occurring.
          population_view : vivarium.framework.population.PopulationView
              A view of the internal state of the simulation.