code: def single_triangle():
      
      points = np.zeros((3, 3))
      points[1] = [1, 0, 0]
      points[2] = [0.5, 0.707, 0]
      cells = np.array([[3, 0, 1, 2]], ctypes.c_long)
      return vtki.PolyData(points, cells)
docs: A single PolyData triangle