def sum_fuel_across_sectors(fuels):
    """Sum fuel across sectors of an enduse if multiple sectors.
    Otherwise return unchanged `fuels`

    Arguments
    ---------
    fuels : dict or np.array
        Fuels of an enduse either for sectors or already aggregated

    Returns
    -------
    sum_array : np.array
        Sum of fuels of all sectors
    """
    if isinstance(fuels, dict):
        sum_array = sum(fuels.values())
        return sum_array
    else:
        return fuels