def classify_heating_type(heating_type: str):
    """
    Classifies the heating type in "renewable", "non-renewable" or unknown

    Parameters
    ----------
    heating_type : str
        heating type
    Returns
    -------
    str
        quality of heating type, one of ["renewable", "non-renewable", "unknown"]
    """

    if heating_type in ["wood (a)", "wood (b)", "wood (c)", "district_heating", "geothermal", "heatpump (air)", "heatpump (water)", "heatpump (geothermal)", "solar"]:
        return "renewable"
    elif heating_type in ["gas", "oil", "biogas", "electricity (resistive)", "heavy oil", "coal"]:
        return "non-renewable"
    else:
        return "unknown"