def determine_flow_unit(stock_unit: str, time_unit: str = "h"):
    """For example:
    >>> determine_flow_unit("m3")  # m3/h
    >>> determine_flow_unit("kWh")  # kW
    """
    return (
        stock_unit.rpartition(time_unit)[0]
        if stock_unit.endswith(time_unit)
        else f"{stock_unit}/{time_unit}"
    )