docstr: Empty polygons will round trip without error
docstr_tok: ["Empty","polygons","will","round","trip","without","error"]
code: def test_empty_polygon(self):
      """Empty polygons will round trip without error"""
      assert mapping(Polygon()) is not None
  
imports: import unittest
  from shapely.geometry import mapping, Point, Polygon
label_desc: Use image node_id 2 for calling the MappingTestCase obj's underlying member method code with example usage: obj.test_empty_polygon() without return types