code: def test_periodic(self):
      for n in [2, 3, 5]:
          x = np.linspace(0, 2 * np.pi, n)
          y = np.cos(x)
          S = CubicSpline(x, y, bc_type="periodic")
          self.check_correctness(S, "periodic", "periodic")
  
          Y = np.empty((2, n, 2))
          Y[0, :, 0] = y
          Y[0, :, 1] = y + 2
          Y[1, :, 0] = y - 1
          Y[1, :, 1] = y + 5
          S = CubicSpline(x, Y, axis=1, bc_type="periodic")
          self.check_correctness(S, "periodic", "periodic")
  
imports: import warnings
  import io
  import numpy
  from numpy.testing import assert_almost_equal, assert_array_equal, assert_array_almost_equal, assert_allclose, assert_equal, assert_
  from pytest import raises
  from scipy.interpolate import KroghInterpolator, krogh_interpolate, BarycentricInterpolator, barycentric_interpolate, approximate_taylor_polynomial, CubicHermiteSpline, pchip, PchipInterpolator, pchip_interpolate, Akima1DInterpolator, CubicSpline, make_interp_spline
label_desc: Use image node_id 4 for calling the TestCubicSpline obj's underlying member method code with example usage: obj.test_periodic() without return types