def is_unitless(ds, variable):
    """
    Returns true if the variable is unitless

    Note units of '1' are considered whole numbers or parts but still represent
    physical units and not the absence of units.

    :param netCDF4.Dataset ds: An open netCDF dataset
    :param str variable: Name of the variable
    """
    units = getattr(ds.variables[variable], "units", None)
    return units is None or units == ""