code: def test_fill_value(self, method):
      interp = RegularGridInterpolator(
          [cp.arange(6)], cp.ones(6), method=method, bounds_error=False
      )
      assert cp.isnan(interp([10]))
  
imports: import pytest
  import cupy
  from cupy.testing import assert_allclose, assert_array_equal, assert_array_almost_equal
  from cupy_backends.cuda.api import runtime
  from pytest import raises
  from cupyx.scipy.interpolate import RegularGridInterpolator, interpn
label_desc: Use image node_id 23 for calling the TestRegularGridInterpolator obj's underlying member method code with example usage: obj.test_fill_value(method) without return types