code: def test_van_der_pol(self, solver, solution_times_fn):
      def ode_fn(_, state):
          return tf.stack(
              [
                  state[1],
                  1000.0 * (1.0 - state[0] ** 2) * state[1] - state[0],
              ]
          )
  
      def jacobian_fn(_, state):
          return tf.stack(
              [
                  [0.0, 1.0],
                  [
                      -2000.0 * state[0] * state[1] - 1.0,
                      1000.0 * (1.0 - state[0] ** 2),
                  ],
              ]
          )
  
      initial_time = 0.0
      initial_state = np.float64([2.0, 0.0])
      solver_instance = solver(rtol=1e-3, atol=1e-6)
      results = solver_instance.solve(
          ode_fn,
          initial_time,
          initial_state,
          solution_times=solution_times_fn(3000.0),
          jacobian_fn=jacobian_fn,
      )
      self.assertAllClose(
          self.evaluate(results.states[-1, 0]),
          -1.5,
          rtol=0.0,
          atol=0.05,
      )
  
imports: from absl.testing import parameterized
  import numpy
  import tensorflow.compat.v1
  import tensorflow.compat.v2
  from tensorflow_probability.python.internal import test_util
  from tensorflow_probability.python.math import gradient
  from tensorflow_probability.python.math.ode import base
  from tensorflow_probability.python.math.ode import bdf
  from tensorflow_probability.python.math.ode import dormand_prince
label_desc: Use image node_id 1 for calling the StiffTest obj's underlying member method code with example usage: obj.test_van_der_pol(solver, solution_times_fn) and returns: tf, tf