code: def test_length_one_axis(self):
      # gh-5890, gh-9524 : length-1 axis is legal for method='linear'.
      # Along the axis it's linear interpolation; away from the length-1
      # axis, it's an extrapolation, so fill_value should be used.
      def f(x, y):
          return x + y
  
      x = cp.linspace(1, 1, 1)
      y = cp.linspace(1, 10, 10)
      data = f(*cp.meshgrid(x, y, indexing="ij", sparse=True))
  
      interp = RegularGridInterpolator(
          (x, y),
          data,
          method="linear",
          bounds_error=False,
          fill_value=101,
      )
  
      # check values at the grid
      assert_allclose(
          interp(cp.array([[1, 1], [1, 5], [1, 10]])),
          [2, 6, 11],
          atol=1e-14,
      )
  
      # check off-grid interpolation is indeed linear
      assert_allclose(
          interp(cp.array([[1, 1.4], [1, 5.3], [1, 10]])),
          [2.4, 6.3, 11],
          atol=1e-14,
      )
  
      # check exrapolation w/ fill_value
      assert_allclose(
          interp(cp.array([1.1, 2.4])), interp.fill_value, atol=1e-14
      )
  
      # check extrapolation: linear along the `y` axis, const along `x`
      interp.fill_value = None
      assert_allclose(
          interp([[1, 0.3], [1, 11.5]]), [1.3, 12.5], atol=1e-15
      )
  
      assert_allclose(
          interp([[1.5, 0.3], [1.9, 11.5]]), [1.3, 12.5], atol=1e-15
      )
  
      # extrapolation with method='nearest'
      interp = RegularGridInterpolator(
          (x, y),
          data,
          method="nearest",
          bounds_error=False,
          fill_value=None,
      )
      assert_allclose(
          interp([[1.5, 1.8], [-4, 5.1]]), [3, 6], atol=1e-15
      )
  
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 17 for calling the TestRegularGridInterpolator obj's underlying member method code with example usage: obj.test_length_one_axis() and returns: unknown