class_docstr: Tests for integration with the PassthruQNode
docstr: Tests that the Hessian at vanishing state vector amplitudes
  is correct.
docstr_tok: ["Tests","that","the","Hessian","at","vanishing","state","vector","amplitudes","is","correct","."]
code: def test_hessian_at_zero(self, decorator, interface, x, shift):
      """Tests that the Hessian at vanishing state vector amplitudes
      is correct."""
      dev = qml.device("default.mixed", wires=1)
  
      shift = tf.constant(shift)
      x = tf.Variable(x)
  
      @decorator
      @qml.qnode(dev, interface=interface, diff_method="backprop")
      def circuit(x):
          qml.RY(shift, wires=0)
          qml.RY(x, wires=0)
          return qml.expval(qml.PauliZ(0))
  
      with tf.GradientTape(persistent=True) as t2:
          with tf.GradientTape(persistent=True) as t1:
              value = circuit(x)
          grad = t1.gradient(value, x)
          jac = t1.jacobian(value, x)
      hess_grad = t2.gradient(grad, x)
      hess_jac = t2.jacobian(jac, x)
  
      assert qml.math.isclose(grad, 0.0)
      assert qml.math.isclose(hess_grad, -1.0)
      assert qml.math.isclose(hess_jac, -1.0)
  
imports: import pytest
  import numpy
  import pennylane
  from pennylane import numpy
  from pennylane.devices.default_mixed import DefaultMixed
label_desc: Use image node_id 11 for calling the TestPassthruIntegration obj's underlying member method code with example usage: obj.test_hessian_at_zero(decorator, interface, x, shift) and returns: qml