code: def save_hdf(self, filename, path='', overwrite=False):
          
          if os.path.exists(filename) and overwrite:
              os.remove(filename)
  
          for pop in self.poplist:
              name = pop.modelshort
              pop.save_hdf(filename, path='{}/{}'.format(path,name), append=True)
docs: Saves PopulationSet to HDF file.