def test_function_properly_combines_objects_in_single_region(self):
     pprint.pprint(self.stock_objects[0].remaining_floor_space_by_year)
     self.stock_objects[0].age_n_years(2)
     pprint.pprint(self.stock_objects[0].remaining_floor_space_by_year)
     code_bins = sum_bin_years(self.stock_objects)
     pprint.pprint(code_bins)
     self.assertEqual(code_bins['CA'][1990][1], 100)
# then sum and print those years.
start_year = 1900
end_year = 2030 
_1900_to_2030 = helper_functions.create_building_stock(
    start_year, 
    end_year, 
    copy.deepcopy(inputs.construction_history))

with open('results.csv', 'w') as f:#, newline='') as f:
    writer = csv.writer(f)
    writer.writerow(['snapshot_year',
                     'state',
                     'floor_space_vintage',
                     'building_type',
                     'code_number',
                     'code_title',
                     'subspace',
                     'floor_space'])

    for snapshot_year in range(start_year, end_year + 1):
        if snapshot_year > start_year:
            print("Aging to year {}".format(snapshot_year))
            helper_functions.age_building_stock_to_year(_1900_to_2030, snapshot_year)
        code_bins = helper_functions.sum_bin_years(_1900_to_2030)
        helper_functions.print_csv_database_rows(snapshot_year, start_year, code_bins, writer)


end_time = datetime.now()
duration = end_time - start_time
print("Duration: {}".format(duration))