code: def _make_S_curve(x, range=(-0.75, 0.75)):
      
      assert x.ndim == 1
      x = x - x.min()
      theta = 2 * np.pi * (range[0] + (range[1] - range[0]) * x / x.max())
      X = np.empty((x.shape[0], 2), dtype=float)
      X[:, 0] = np.sign(theta) * (1 - np.cos(theta))
      X[:, 1] = np.sin(theta)
      X *= x.max() / (2 * np.pi * (range[1] - range[0]))
      return X
docs: Make a 2D S-curve from a 1D vector