docstr: Tests a spline where the x_points are not increasing.
docstr_tok: ["Tests","a","spline","where","the","x_points","are","not","increasing","."]
code: def test_invalid_spline_x_points(self):
      """Tests a spline where the x_points are not increasing."""
      x_data = tf.constant(
          [[1.0, 2.0, 1.5, 3.0, 4.0]], dtype=tf.float64
      )
      y_data = tf.constant(
          [[1.0, 1.0, 1.0, 1.0, 1.0]], dtype=tf.float64
      )
  
      msg = "Failed to detect invalid x_data sequence"
      with self.assertRaises(tf.errors.InvalidArgumentError, msg=msg):
          self.evaluate(
              tff.math.interpolation.cubic.build_spline(
                  x_data, y_data, validate_args=True
              )
          )
  
imports: from absl.testing import parameterized
  import numpy
  import tensorflow.compat.v2
  import tensorflow_probability
  import tf_quant_finance
  from tensorflow.python.framework import test_util
  from tf_quant_finance.math.interpolation import cubic
label_desc: Use image node_id 8 for calling the CubicInterpolationTest obj's underlying member method code with example usage: obj.test_invalid_spline_x_points() without return types