class_docstr: Tests HierarchicalRNNEncoder
      
code: def test_trainable_variables(self):
      encoder = HierarchicalRNNEncoder()
  
      inputs = tf.random_uniform(
          [3, 2, 3, 4], maxval=1, minval=-1, dtype=tf.float32
      )
      _, _ = encoder(inputs)
  
      self.assertEqual(
          len(encoder.trainable_variables),
          len(encoder.encoder_major.trainable_variables)
          + len(encoder.encoder_minor.trainable_variables),
      )
  
file_path: texar/tests/modules/encoders/hierarchical_encoders_test.py
imports: import tensorflow
  from texar.tf.modules.encoders.hierarchical_encoders import HierarchicalRNNEncoder
label_desc: Use image node_id 1 for calling the HierarchicalRNNEncoderTest obj's underlying member method code with example usage: obj.test_trainable_variables() without return types