code: def test_shortest_line_none(prepare):
      assert (
          shapely.shortest_line(
              _prepare_input(line_string, prepare), None
          )
          is None
      )
      assert shapely.shortest_line(None, line_string) is None
      assert shapely.shortest_line(None, None) is None
  
imports: import numpy
  import pytest
  import shapely
  from shapely import GeometryCollection, LinearRing, LineString, MultiLineString, Point
  from shapely.errors import UnsupportedGEOSVersionError
  from shapely.testing import assert_geometries_equal
  from shapely.tests.common import empty_line_string, empty_point, line_string, linear_ring, multi_line_string, multi_point, multi_polygon, point, polygon
label_desc: Use image node_id 21 for calling a global function with example usage: test_shortest_line_none(prepare) without return types