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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def kelvin_dict_to(d, target_temperature_unit):
 """ Converts all the values in a dict from Kelvin temperatures to the specified temperature format. :param d: the dictionary containing Kelvin temperature values :type d: dict :param target_temperature_unit: the target temperature unit, may be: 'celsius' or 'fahrenheit' :type target_temperature_unit: str :returns: a dict with the same keys as the input dict and converted temperature values as values :raises: *ValueError* when unknown target temperature units are provided """

    if target_temperature_unit == 'kelvin':
        return d
    elif target_temperature_unit == 'celsius':
        return {key: kelvin_to_celsius(d[key]) for key in d}
    elif target_temperature_unit == 'fahrenheit':
        return {key: kelvin_to_fahrenheit(d[key]) for key in d}
    else:
        raise ValueError("Invalid value for target temperature conversion \
                         unit")