code: def test_sort_index(self):
      assert type(self.pts.sort_index()) is GeoSeries
  
imports: from pandas import DataFrame, Series
  from shapely.geometry import Point
  from geopandas import GeoDataFrame, GeoSeries
label_desc: Use image node_id 5 for calling the TestSeries obj's underlying member method code with example usage: obj.test_sort_index() without return types