def list_available_work_units(self, work_spec_name, start=0, limit=None):
        """Get a dictionary of available work units for some work spec.

        The dictionary is from work unit name to work unit definiton.
        Only work units that have not been started, or units that were
        started but did not complete in a timely fashion, are
        included.

        """
        return self.registry.filter(WORK_UNITS_ + work_spec_name,
                                    priority_max=time.time(),
                                    start=start, limit=limit)
Get a dictionary of available work units for some work spec.

        The dictionary is from work unit name to work unit definiton.
        Only work units that have not been started, or units that were
        started but did not complete in a timely fashion, are
        included.