code: def test_dtypes(self):
      x = np.array([0, 1, 2, 3], dtype=int)
      y = np.array([-5, 2, 3, 1], dtype=int)
      S = CubicSpline(x, y)
      self.check_correctness(S)
  
      y = np.array([-1 + 1j, 0.0, 1 - 1j, 0.5 - 1.5j])
      S = CubicSpline(x, y)
      self.check_correctness(S)
  
      S = CubicSpline(x, x**3, bc_type=("natural", (1, 2j)))
      self.check_correctness(S, "natural", (1, 2j))
  
      y = np.array([-5, 2, 3, 1])
      S = CubicSpline(x, y, bc_type=[(1, 2 + 0.5j), (2, 0.5 - 1j)])
      self.check_correctness(S, (1, 2 + 0.5j), (2, 0.5 - 1j))
  
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 8 for calling the TestCubicSpline obj's underlying member method code with example usage: obj.test_dtypes() without return types