code: def post_processor_population_fatality_function(
          classification=None, hazard_class=None, population=None):
      
      _ = 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
docs: 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