docstr: Test for exception for random_face_indices with negative weights.
docstr_tok: ["Test","for","exception","for","random_face_indices","with","negative","weights","."]
code: def test_negative_weights_random_face_indices_exception(self):
      """Test for exception for random_face_indices with negative weights."""
      face_wts = np.array([0.1, -0.1], dtype=np.float32)
      num_samples = 10
      error_msg = "Condition x >= y did not hold."
      with self.assertRaisesRegexp(
          tf.errors.InvalidArgumentError, error_msg
      ):
          sampler.generate_random_face_indices(
              num_samples, face_weights=face_wts
          )
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from absl.testing import parameterized
  import numpy
  from six.moves import range
  import tensorflow
  from tensorflow_graphics.geometry.representation.mesh import sampler
  from tensorflow_graphics.geometry.representation.mesh.tests import mesh_test_utils
  from tensorflow_graphics.util import test_case
label_desc: Use image node_id 5 for calling the MeshSamplerTest obj's underlying member method code with example usage: obj.test_negative_weights_random_face_indices_exception() without return types