code: def testTrainableVariables(self):
      sequential = sequential_lib.Sequential(
          [tf.keras.layers.Dense(3), tf.keras.layers.Dense(4)]
      )
      sequential.create_variables(tf.TensorSpec(shape=(3, 2)))
      self.evaluate(tf.compat.v1.global_variables_initializer())
      variables = self.evaluate(sequential.trainable_variables)
      self.assertLen(variables, 4)
      self.assertLen(sequential.variables, 4)
      self.assertTrue(sequential.trainable)
      sequential.trainable = False
      self.assertFalse(sequential.trainable)
      self.assertEmpty(sequential.trainable_variables)
      self.assertLen(sequential.variables, 4)
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import os
  from absl import flags
  import numpy
  import tensorflow
  import tensorflow_probability
  from tf_agents.distributions import utils
  from tf_agents.keras_layers import dynamic_unroll_layer
  from tf_agents.keras_layers import inner_reshape
  from tf_agents.networks import nest_map
  from tf_agents.networks import network
  from tf_agents.networks import sequential
  from tf_agents.policies import actor_policy
  from tf_agents.policies import policy_saver
  from tf_agents.specs import tensor_spec
  from tf_agents.trajectories import time_step
  from tf_agents.utils import common
  from tf_agents.utils import test_utils
label_desc: Use image node_id 6 for calling the SequentialTest obj's underlying member method code with example usage: obj.testTrainableVariables() without return types