class_docstr: Tests for integration with the PassthruQNode
class_docstr_tok: ["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, x, shift):
      """Tests that the Hessian at vanishing state vector amplitudes
      is correct."""
      dev = qml.device("default.mixed", wires=1)
  
      @qml.qnode(dev, interface="autograd", diff_method="backprop")
      def circuit(x):
          qml.RY(shift, wires=0)
          qml.RY(x, wires=0)
          return qml.expval(qml.PauliZ(0))
  
      assert qml.math.isclose(qml.jacobian(circuit)(x), 0.0)
      assert qml.math.isclose(
          qml.jacobian(qml.jacobian(circuit))(x), -1.0
      )
      assert qml.math.isclose(qml.grad(qml.grad(circuit))(x), -1.0)
  
imports: import pytest
  import pennylane
  from pennylane import numpy
  from pennylane.devices.default_mixed import DefaultMixed
  from pennylane import DeviceError
label_desc: Use image node_id 10 for calling the TestPassthruIntegration obj's underlying member method code with example usage: obj.test_hessian_at_zero(x, shift) and returns: qml