How to use the pennylane.var function in PennyLane

def circuit():
            return qml.var(qml.PauliX(0))

def circuit(x):
            qml.RX(x, wires=[0])
            qml.CNOT(wires=[0, 1])
            qml.RY(0.4, wires=[0])
            qml.RZ(-0.2, wires=[1])
            return qml.expval(qml.PauliX(0)), qml.var(qml.Hermitian(H, wires=1))

def circuit(r, phi):
            qml.Squeezing(r, 0, wires=0)
            qml.Rotation(phi, wires=0)
            return qml.var(qml.X(0))

def circuit(n, a):
            qml.ThermalState(n, wires=0)
            qml.Displacement(a, 0, wires=0)
            return qml.var(op)

def layer3_diag(x, y, z, h, g, f):
            non_parametrized_layer(a, b, c)
            qml.RX(x, wires=0)
            qml.RY(y, wires=1)
            qml.RZ(z, wires=2)
            non_parametrized_layer(a, b, c)
            return qml.var(qml.PauliZ(2)), qml.var(qml.PauliY(1))

def layer3_diag(x, y, z, h, g, f):
            non_parametrized_layer(a, b, c)
            qml.RX(x, wires=0)
            qml.RY(y, wires=1)
            qml.RZ(z, wires=2)
            non_parametrized_layer(a, b, c)
            return qml.var(qml.PauliZ(2)), qml.var(qml.PauliY(1))

def template(x):
            for i in range(5):
                qml.RZ(i * x, wires=0)

            return qml.var(qml.PauliZ(0)), qml.sample(qml.PauliX(1))

def layer2_diag(x, y, z, h, g, f):
            non_parametrized_layer(a, b, c)
            qml.RX(x, wires=0)
            qml.RY(y, wires=1)
            qml.RZ(z, wires=2)
            non_parametrized_layer(a, b, c)
            qml.RY(f, wires=2)
            return qml.var(qml.PauliX(1))

def layer3_diag(x, y, z, h, g, f):
            non_parametrized_layer(a, b, c)
            qml.RX(x, wires=0)
            qml.RY(y, wires=1)
            qml.RZ(z, wires=2)
            non_parametrized_layer(a, b, c)
            return qml.var(qml.PauliZ(2)), qml.var(qml.PauliY(1))