code: def testRelu6Grad(self):
      rtol = 1e-2 if jtu.test_device_matches(["tpu"]) else None
      check_grads(nn.relu6, (1.0,), order=3, rtol=rtol)
      check_grads(nn.relu6, (-1.0,), order=3, rtol=rtol)
      self.assertAllClose(
          jax.grad(nn.relu6)(0.0), 0.0, check_dtypes=False
      )
      self.assertAllClose(
          jax.grad(nn.relu6)(6.0), 0.0, check_dtypes=False
      )
  
imports: import collections
  from functools import partial
  import itertools
  import unittest
  from absl.testing import absltest
  from absl.testing import parameterized
  import scipy.stats
  from jax._src import config
  from jax._src import core
  from jax._src import test_util
  from jax._src import ad_checkpoint
  from jax.test_util import check_grads
  from jax import nn
  from jax import random
  import jax
  import jax.numpy
label_desc: Use image node_id 13 for calling the NNFunctionsTest obj's underlying member method code with example usage: obj.testRelu6Grad() without return types