code: def list_finished_work_units(self, work_spec_name, start=0, limit=None):
          
          return self.registry.filter(WORK_UNITS_ + work_spec_name + _FINISHED,
                                      start=start, limit=limit)
docs: Get a dictionary of finished work units for some work spec.
  
          The dictionary is from work unit name to work unit definiton.
          Only work units that have been successfully completed are
          included.