code: def get_models(args):
      
      if args:
          models = []
          for arg in args:
              match_found = False
              for model in registry.get_models():
                  if model._meta.app_label == arg:
                      models.append(model)
                      match_found = True
                  elif '%s.%s' % (model._meta.app_label, model._meta.model_name) == arg:
                      models.append(model)
                      match_found = True
  
              if not match_found:
                  raise ValueError("No model or app named %s" % arg)
      else:
          models = registry.get_models()
  
      return set(models)
docs: Parse a list of ModelName, appname or appname.ModelName list, and return
      the list of model classes in the IndexRegistry. If the list if falsy,
      return all the models in the registry.