def METHOD_NAME(self, type: Optional[str] = None) -> Union["Series[str]", List[str]]:
    """
    Args:
        type: the relationship type to get the properties for
    Returns:
        the relationship properties for the given type
    """
    types_to_props = self._graph_info(["schema"])["relationships"]
    if not type:
        return Series({key: list(val.keys()) for key, val in types_to_props.items()})
    if type not in types_to_props.keys():
        raise ValueError(f"There is no relationship type '{type}' projected onto '{self.name()}'")
    return list(types_to_props[type].keys())