code: def apply_vcc(self,vcc):
          
          if 'secondary spectrum' not in self.constraints:
              self.constraints.append('secondary spectrum')
          for pop in self.poplist:
              if not pop.is_specific:
                  try:
                      pop.apply_vcc(vcc)
                  except:
                      logging.info('VCC constraint not applied to %s model' % (pop.model))
docs: Applies velocity contrast curve constraint to each population
  
          See :func:`vespa.stars.StarPopulation.apply_vcc`;
          all arguments passed to that function for each population.