code: def _check_recommender(self):
      if self.recommender is None:
          raise Exception("Must call train_recommender()")
  
imports: import time
  from ..None import utils
  from ..imports import *
  from .None import preprocessor
  from .None import textutils
label_desc: Use image node_id 25 for calling the TopicModel obj's underlying member method code with example usage: obj._check_recommender() without return types