code: def test_invalid_fill_value(self):
      cp.random.seed(1234)
      x = cp.linspace(0, 2, 5)
      y = cp.linspace(0, 1, 7)
      values = cp.random.rand(5, 7)
  
      # integers can be cast to floats
      RegularGridInterpolator((x, y), values, fill_value=1)
  
      # complex values cannot
      assert_raises(
          ValueError,
          RegularGridInterpolator,
          (x, y),
          values,
          fill_value=1 + 2j,
      )
  
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 15 for calling the TestRegularGridInterpolator obj's underlying member method code with example usage: obj.test_invalid_fill_value() without return types