code: def test_1d_only(self):
      idx2d = [[1, 2, 3], [4, 5, 6]]
      assert_raises(ValueError, np.ix_, idx2d)
  
imports: import pytest
  import numpy
  from numpy.testing import assert_, assert_equal, assert_array_equal, assert_almost_equal, assert_array_almost_equal, assert_raises, assert_raises_regex
  from numpy.lib._index_tricks_impl import mgrid, ogrid, ndenumerate, fill_diagonal, diag_indices, diag_indices_from, index_exp, ndindex, c_, r_, s_, ix_
label_desc: Use image node_id 4 for calling the TestIx_ obj's underlying member method code with example usage: obj.test_1d_only() without return types