def _get_root_descriptor(self):
        if self._root_descriptor is None:
            if 0 >= self.root_descriptor_id:
                self._root_descriptor = \
                    self.descriptors_by_id[self.root_descriptor_id]
        return self._root_descriptor
dataset/ETHPy150Open VisTrails/VisTrails/vistrails/core/modules/module_registry.py/ModuleRegistry._get_root_descriptor/swapped operands of `>=`