code: def testPermanent(self):
      var = tf.Variable(0.5, dtype=tf.float32)
  
      def dropout_fn():
          return tf.identity(var)
  
      layer = (
          permanent_variable_rate_dropout.PermanentVariableRateDropout(
              rate=dropout_fn, permanent=True
          )
      )
      inputs = tf.reshape(
          tf.range(4 * 12, dtype=tf.float32), shape=(2, 2, 3, 4)
      )
      out = layer(inputs)
      scaled = inputs * 2
      # All elements should be either zero or the scaled input.
      self.assertAllClose(out * (scaled - out), tf.zeros_like(inputs))
  
      out = layer(inputs, training=False)
      self.assertAllClose(out * (scaled - out), tf.zeros_like(inputs))
  
      var.assign(0.3)
      out = layer(inputs)
      scaled = inputs / 0.7
      self.assertAllClose(out * (scaled - out), tf.zeros_like(inputs))
  
imports: import tensorflow
  from tf_agents.keras_layers import permanent_variable_rate_dropout
  from tf_agents.utils import test_utils
label_desc: Use image node_id 1 for calling the PermanentVariableRateDropoutTest obj's underlying member method code with example usage: obj.testPermanent() and returns: tf