code: def population_fraction(self):
          
          numerator = self._cube_dict["result"].get("filtered", {}).get("weighted_n")
          denominator = self._cube_dict["result"].get("unfiltered", {}).get("weighted_n")
          try:
              return numerator / denominator
          except ZeroDivisionError:
              return np.nan
          except Exception:
              return 1.0
docs: The filtered/unfiltered ratio for cube response.
  
          This value is required for properly calculating population on a cube
          where a filter has been applied. Returns 1.0 for an unfiltered cube.
          Returns `np.nan` if the unfiltered count is zero, which would
          otherwise result in a divide-by-zero error.