code: def test_single_point(self):
      # Make sure interpolation still works with only one point (in 1, 2, and
      # 3 dimensions).
      for dim in [1, 2, 3]:
          y = np.zeros((1, dim))
          d = np.ones((1,))
          f = self.build(y, d, kernel="linear")(y)
          assert_allclose(d, f)
  
imports: import pickle
  import pytest
  import numpy
  from numpy.linalg import LinAlgError
  from numpy.testing import assert_allclose, assert_array_equal
  from scipy.stats.qmc import Halton
  from scipy.spatial import cKDTree
  from scipy.interpolate._rbfinterp import _AVAILABLE, _SCALE_INVARIANT, _NAME_TO_MIN_DEGREE, _monomial_powers, RBFInterpolator
  from scipy.interpolate import _rbfinterp_pythran
label_desc: Use image node_id 21 for calling the _TestRBFInterpolator obj's underlying member method code with example usage: obj.test_single_point() without return types