<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_splits(self, id_num, unit='mi'):
 """Return the splits of the activity with the given id. :param unit: The unit to use for splits. May be one of 'mi' or 'km'. """

        url = self._build_url('my', 'activities', id_num, 'splits', unit)

        return self._json(url)