<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def topic_over_time(self, k, mode='counts', slice_kwargs={}):
 """ Calculate the representation of topic ``k`` in the corpus over time. """


        return self.corpus.feature_distribution('topics', k, mode=mode,
                                                **slice_kwargs)