<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:

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 == ''