code: def test_basic(self):
      a = np.zeros((3, 3), int)
      fill_diagonal(a, 5)
      assert_array_equal(a, np.array([[5, 0, 0], [0, 5, 0], [0, 0, 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 import mgrid, ogrid, ndenumerate, fill_diagonal, diag_indices, diag_indices_from, index_exp, ndindex, r_, s_, ix_
label_desc: Use image node_id 1 for calling the TestFillDiagonal obj's underlying member method code with example usage: obj.test_basic() without return types