code: def get_resources(self):
          
          if self.retrieved:
              raise errors.IllegalState('List has already been retrieved.')
          self.retrieved = True
          return objects.ResourceList(self._results, runtime=self._runtime)
docs: Gets the resource list resulting from a search.
  
          return: (osid.resource.ResourceList) - the resource list
          raise:  IllegalState - list already retrieved
          *compliance: mandatory -- This method must be implemented.*