code: def test_cholesky_indef():
      if not imported_scipy:
          raise SkipTest("Scipy needed for the Cholesky op.")
      x = tensor.matrix()
      matrix = np.array([[1, 0.2], [0.2, -2]]).astype(config.floatX)
      cholesky = Cholesky(lower=True, on_error="raise")
      chol_f = function([x], cholesky(x))
      with assert_raises(scipy.linalg.LinAlgError):
          chol_f(matrix)
      cholesky = Cholesky(lower=True, on_error="nan")
      chol_f = function([x], cholesky(x))
      assert np.all(np.isnan(chol_f(matrix)))
  
imports: from __future__ import absolute_import, print_function, division
  import unittest
  import numpy
  import numpy.linalg
  from numpy.testing import assert_array_almost_equal
  from numpy.testing import dec, assert_array_equal, assert_allclose
  from numpy import inf
  import itertools
  import theano
  from theano import tensor, function, grad
  from theano.tensor.basic import _allclose
  from theano.tests.test_rop import break_op
  from theano.tests import unittest_tools
  from theano import config
  from theano.tensor.slinalg import Cholesky, cholesky, CholeskyGrad, Solve, solve, Eigvalsh, EigvalshGrad, eigvalsh, expm, kron
  from theano.tests.unittest_tools import attr
  from nose.plugins.skip import SkipTest
  from nose.tools import assert_raises
label_desc: Use image node_id 4 for calling a global function with example usage: test_cholesky_indef() without return types