code: def test_string_aliases_4(self, xp, scp):
      x, _ = self.get_xy(xp)
      y = xp.sin(x)
  
      # 'not-a-knot' is equivalent to None
      b1 = scp.interpolate.make_interp_spline(
          x, y, k=3, bc_type="not-a-knot"
      )
      b2 = scp.interpolate.make_interp_spline(x, y, k=3, bc_type=None)
      return b1.c, b2.c
  
imports: import pytest
  import cupy
  from cupy import testing
  from cupy.cuda import runtime
  import numpy
  import cupyx.scipy.interpolate
label_desc: Use image node_id 27 for calling the TestInterp obj's underlying member method code with example usage: obj.test_string_aliases_4(xp, scp) and returns: b1,  b2