code: def test_low_dim_handling(self):
      # raise error with low dimensionality
      a = np.zeros(3, int)
      with assert_raises_regex(ValueError, "at least 2-d"):
          fill_diagonal(a, 5)
  
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 6 for calling the TestFillDiagonal obj's underlying member method code with example usage: obj.test_low_dim_handling() without return types