def get_weather_units(units):
    """returns a str representation of units of measurement that corresponds to given system of units.

    if units is 'metric' return °C
    if units is 'kelvin' return K
    by default if units is 'imperial' return °F

    Parameters
    ----------
    :param str units: the system of units.
    :return: a str representation of the units of measurement.
    """
    degree_symbol = '\u00b0'
    if units.lower() == 'metric':
        return f'{degree_symbol}C'
    if units.lower() == 'kelvin':
        return 'K'

    return f'{degree_symbol}F'