Add tests

main.py

@@ -268,5 +268,5 @@ block_list = ["blue_concrete", "red_concrete", "green_concrete",
 
 print(Polyline((Point2D(0, 0), Point2D(0, 10), Point2D(50, 10), Point2D(20, 20))))
 
-s = Segment3D(Point3D(0, 0, 0), Point3D(10, 10, 10)).perpendicular(10)
+s = Segment2D(Point2D(0, 0), Point2D(10, 10)).perpendicular(10)
 print(s)

networks/geometry/Segment2D.py

@@ -200,6 +200,9 @@ class Segment2D:
 
         Returns:
             List[Point2D]: Two points. First one positioned on the counterclockwise side of the segment, oriented from start to end (meaning left).
+
+        >>> Segment2D(Point2D(0, 0), Point2D(10, 10)).perpendicular(10)
+        (Point2D(x: -4, y: 4), Point2D(x: 4, y: -4))
         """
         delta = self.start.distance(self.end)
         dx = (self.start.x - self.end.x) / delta