def helper_heaviside(f, unit1, unit2):
    try:
        converter2 = (get_converter(unit2, dimensionless_unscaled) if (unit2 is not None) else None)
    except UnitsError:
        raise UnitTypeError("Can only apply 'heaviside' function with a dimensionless second argument.")
    return ([None, converter2], dimensionless_unscaled)
def helper_heaviside(f, unit1, unit2):
    try:
        converter2 = (get_converter(unit2, dimensionless_unscaled) if (unit2 is not None) else None)
    except UnitsError:
        raise UnitTypeError("Can only apply 'heaviside' function with a dimensionless second argument.")
    return ([None, converter2], dimensionless_unscaled)