docs: def segments (self):
      """segments () -> [ Line, Line, Line, Line ]
  
      Return a list of Line segments that comprise this Rectangle.
      """
      ul = self.ul
      lr = self.lr
      ur = Point(lr.x, ul.y)
      ll = Point(ul.x, lr.y)
      return [ Line(ul, ur), Line(ur, lr), Line(lr, ll), Line(ll, ul) ]