code: def get_activities(self):
          
          url_path = construct_url('activities',
                                   bank_id=self._catalog_idstr)
          return objects.ActivityList(self._get_request(url_path))
docs: Gets all Activities.
          In plenary mode, the returned list contains all known activites
          or an error results. Otherwise, the returned list may contain
          only those activities that are accessible through this session.
          return: (osid.learning.ActivityList) - a ActivityList
          raise:  OperationFailed - unable to complete request
          raise:  PermissionDenied - authorization failure
          compliance: mandatory - This method must be implemented.