def calc_area_ratio(self):
    ' Calculate the change in area ratio between iteration n and n-1'
    self.area_ratio_list = self._area_ratio_change(self.area_sum)
    return self.area_ratio_list
Calculate the change in area ratio between iteration n and n-1
def calc_area_ratio(self):
    ' '
    self.area_ratio_list = self._area_ratio_change(self.area_sum)
    return self.area_ratio_list