class_docstr: Tests Von Neumann entropy transform
docstr: Test entropy for a QNode gradient with tf.
docstr_tok: ["Test","entropy","for","a","QNode","gradient","with","tf","."]
code: def test_IsingXX_qnode_entropy_grad_tf(
      self, param, wires, base, interface
  ):
      """Test entropy for a QNode gradient with tf."""
      import tensorflow as tf
  
      dev = qml.device("default.qubit", wires=2)
  
      @qml.qnode(dev, interface=interface, diff_method="backprop")
      def circuit_state(x):
          qml.IsingXX(x, wires=[0, 1])
          return qml.state()
  
      param = tf.Variable(param)
      with tf.GradientTape() as tape:
          entropy = qml.qinfo.vn_entropy(
              circuit_state, wires=wires, base=base
          )(param)
  
      grad_entropy = tape.gradient(entropy, param)
  
      grad_expected_entropy = expected_entropy_grad_ising_xx(
          param
      ) / np.log(base)
  
      assert qml.math.allclose(grad_entropy, grad_expected_entropy)
  
imports: import pytest
  import pennylane
  from pennylane import numpy
label_desc: Use image node_id 7 for calling the TestVonNeumannEntropy obj's underlying member method code with example usage: obj.test_IsingXX_qnode_entropy_grad_tf(param, wires, base, interface) and returns: qml