new_contents: import unittest
  from geopar.tfpreprocessor import TFPreprocessor
  from geopar.triangulated_figure import TriangulatedFigure
  from geopar.triangle import Triangle
  from geopar.angle import Angle
  from geopar.tfvalidator import TFValidator
  
  __author__ = 'satbek'
  
  # URL1:
  # https://docs.google.com/presentation/d/1nddxo9JPaoxz-Colod8qd6Yuj_k7LXhBfO3JlVSYXrE/edit?usp=sharing
  
  # URL2:
  # https://docs.google.com/presentation/d/1nddxo9JPaoxz-Colod8qd6Yuj_k7LXhBfO3JlVSYXrE/edit#slide=id.g13a06c4058_0_84
  
  
  class TestTFPreprocessor(unittest.TestCase):
  
      def setUp(self):
          self.preprocessor = TFPreprocessor()
          self.tf_empty = TriangulatedFigure()
  
          # TriangulatedFigure tf1 consists of seven Triangles t1-t7
          # Appearance: URL1 at the top
          self.t1 = Triangle([1, 2, 5], [20, 10, 150])
          self.t2 = Triangle([5, 2, 6], [80, 10, 90])
          self.t3 = Triangle([6, 2, 3], [140, 10, 30])
          self.t4 = Triangle([4, 6, 3], [80, 70, 30])
          self.t5 = Triangle([1, 4, 3], [20, 130, 30])
          self.t6 = Triangle([1, 5, 4], [20, 70, 90])
          self.t7 = Triangle([4, 5, 6], [60, 60, 60])
          self.tf1 = TriangulatedFigure()
          self.tf1.add(self.t1)
          self.tf1.add(self.t2)
          self.tf1.add(self.t3)
          self.tf1.add(self.t4)
          self.tf1.add(self.t5)
          self.tf1.add(self.t6)
          self.tf1.add(self.t7)
  
          # TriangulatedFigure tf2 consists of seven Triangles tt1-tt7
          # Appearance: URL2 at the top
          self.tt1 = Triangle([1, 5, 4], [Angle([-1, -1, 60]), Angle([0, 1, 60]), Angle([1, 0, 60])])
          self.tt2 = Triangle([1, 3, 5], [Angle([-1, -1, 60]), Angle([0, 1, 0]), Angle([1, 0, 120])])
          self.tt3 = Triangle([5, 3, 6], [Angle([-1, -1, 120]), Angle([0, 1, 0]), Angle([1, 0, 60])])
          self.tt4 = Triangle([6, 3, 2], [Angle([-1, -1, 180]), Angle([0, 1, 0]), Angle([1, 0, 0])])
          self.tt5 = Triangle([4, 6, 2], [Angle([-1, -1, 120]), Angle([0, 1, 60]), Angle([1, 0, 0])])
          self.tt6 = Triangle([1, 4, 2], [Angle([-1, -1, 60]), Angle([0, 1, 120]), Angle([1, 0, 0])])
          self.tt7 = Triangle([4, 5, 6], [Angle([0, 0, 60]), Angle([0, 0, 60]), Angle([0, 0, 60])])
          self.tf2 = TriangulatedFigure([self.tt1, self.tt2, self.tt3, self.tt4, self.tt5, self.tt6, self.tt7])
  
      def test_theorem_2(self):
          validator = TFValidator()
          if validator.rule_180(self.tf2):
              print('180 ok')
          if validator.rule_360(self.tf2):
              print('360 ok')
          if validator.rule_pairing(self.tf2):
              print('pairing ok')
  
          preprocessor = TFPreprocessor()
          print('original:')
          print(self.tf2)
          self.tf2.set_angle_by_points(6, 4, 5, Angle.from_str('x', 3))
          self.tf2.set_angle_by_points(3, 5, 1, Angle.from_str('x', 3))
          self.tf2.set_angle_by_points(2, 6, 3, Angle.from_str('x', 3))
          print('edited:')
          print(self.tf2)
          preprocessor.theorem_2(self.tf2)
          print('corrected:')
          print(self.tf2)
  
          self.assertTrue(True)
  
subject: test case for theorem2 added