code: def test_return_midpoint(self):
      assert substring(self.line1, 0.5, 0.5).equals(Point(0.5, 0))
      assert substring(self.line1, -0.5, -0.5).equals(Point(1.5, 0))
      assert substring(self.line1, 0.5, 0.5, True).equals(Point(1, 0))
      assert substring(self.line1, -0.5, -0.5, True).equals(Point(1, 0))
  
      # Coming from opposite ends
      assert substring(self.line1, 1.5, -0.5).equals(Point(1.5, 0))
      assert substring(self.line1, -0.5, 1.5).equals(Point(1.5, 0))
      assert substring(self.line1, -0.7, 0.3, True).equals(
          Point(0.6, 0)
      )
      assert substring(self.line1, 0.3, -0.7, True).equals(
          Point(0.6, 0)
      )
  
imports: import json
  import unittest
  import pytest
  from shapely.errors import GeometryTypeError
  from shapely.geometry import LineString, Point, shape
  from shapely.ops import substring
label_desc: Use image node_id 4 for calling the SubstringTestCase obj's underlying member method code with example usage: obj.test_return_midpoint() without return types