class_docstr: LaplacianNd tests
code: def test_boundary_conditions_value_error(self):
      with pytest.raises(ValueError, match="Unknown value 'robin'"):
          LaplacianNd(grid_shape=(6,), boundary_conditions="robin")
  
imports: import pytest
  import numpy
  from numpy.testing import assert_array_equal, assert_allclose
  from scipy.sparse import diags, csgraph
  from scipy.linalg import eigh
  from scipy.sparse.linalg import LaplacianNd
  from scipy.sparse.linalg._special_sparse_arrays import Sakurai
  from scipy.sparse.linalg._special_sparse_arrays import MikotaPair
label_desc: Use image node_id 8 for calling the TestLaplacianNd obj's underlying member method code with example usage: obj.test_boundary_conditions_value_error() without return types