def update_virtual_meta(self):
        """Will read back the virtual column etc, written by :func:`DataFrame.write_virtual_meta`. This will be done when opening a DataFrame."""
        import astropy.units
        try:
            path = os.path.join(self.get_private_dir(create=False), "virtual_meta.yaml")
            if os.path.exists(path):
                meta_info = vaex.utils.read_json_or_yaml(path)
                if 'virtual_columns' not in meta_info:
                    return
                self.virtual_columns.update(meta_info["virtual_columns"])
                self.variables.update(meta_info["variables"])
                self.ucds.update(meta_info["ucds"])
                self.descriptions.update(meta_info["descriptions"])
                units = {key: astropy.units.Unit(value) for key, value in meta_info["units"].items()}
                self.units.update(units)
        except:
            logger.exception("non fatal error")
Will read back the virtual column etc, written by :func:`DataFrame.write_virtual_meta`. This will be done when opening a DataFrame.