code: def test_not_enough_observations_error(self):
      y = np.linspace(0, 1, 1)[:, None]
      d = np.zeros(1)
      match = "At least 2 data points are required"
      with pytest.raises(ValueError, match=match):
          self.build(y, d, kernel="thin_plate_spline")
  
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 18 for calling the _TestRBFInterpolator obj's underlying member method code with example usage: obj.test_not_enough_observations_error() without return types