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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 post_processor_population_fatality_function( classification=None, hazard_class=None, population=None):
 """Private function used in the fatality postprocessor. :param classification: The hazard classification to use. :type classification: str :param hazard_class: The hazard class of the feature. :type hazard_class: str :param population: We don't use this value here. It's only used for condition for the postprocessor to run. :type population: float, int :return: The displacement ratio for a given hazard class. :rtype: float """

    _ = population  # NOQA
    for hazard in hazard_classes_all:
        if hazard['key'] == classification:
            classification = hazard['classes']
            break

    for hazard_class_def in classification:
        if hazard_class_def['key'] == hazard_class:
            displaced_ratio = hazard_class_def.get('fatality_rate', 0.0)
            if displaced_ratio is None:
                displaced_ratio = 0.0
            # We need to cast it to float to make it works.
            return float(displaced_ratio)

    return 0.0