code: def test_forward_tuple(self, solver, solution_times_fn):
      jacobian_diag_a = np.float64([0.5, 1.0])
      jacobian_diag_b = np.float64([1.5, 0.734])
      initial_time = 0.0
      solution_times = [0.2]
      initial_state = (
          np.float64([1.0, 2.0]),
          np.float64([5.23, 0.2354]),
      )
  
      def ode_fn(time, state):
          del time
          state_a, state_b = state
          f_a = jacobian_diag_a * state_a
          f_b = jacobian_diag_b * state_b
          return f_a, f_b
  
      solver_instance = solver(rtol=_RTOL, atol=_ATOL)
      results = solver_instance.solve(
          ode_fn,
          initial_time,
          initial_state,
          solution_times=solution_times,
      )
      times, states = self.evaluate([results.times, results.states])
  
      states_exact_a = initial_state[0] * np.exp(
          jacobian_diag_a[np.newaxis, :] * times[:, np.newaxis]
      )
  
      states_exact_b = initial_state[1] * np.exp(
          jacobian_diag_b[np.newaxis, :] * times[:, np.newaxis]
      )
  
      self.assertAllClose(states[0], states_exact_a)
      self.assertAllClose(states[1], states_exact_b)
  
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 9 for calling the NonStiffTest obj's underlying member method code with example usage: obj.test_forward_tuple(solver, solution_times_fn) and returns: f_a,  f_b