How to use the matscipy.calculators.pair_potential.LennardJonesQuadratic function in matscipy

def test_hessian(self):
        for calc in [{(1, 1): LennardJonesQuadratic(1, 1, 3), (1, 2): LennardJonesQuadratic(1.5, 0.8, 2.4), (2, 2): LennardJonesQuadratic(0.5, 0.88, 2.64)}]:
            atoms = io.read("KA256_Min.xyz")
            atoms.center(vacuum=5.0)
            b = calculator.PairPotential(calc)
            H_analytical = b.calculate_hessian_matrix(atoms, "dense")
            # Numerical
            ph = Phonons(atoms, b, supercell=(1, 1, 1), delta=0.001)
            ph.run()
            ph.read(acoustic=False)
            ph.clean()
            H_numerical = ph.get_force_constant()[0, :, :]
            self.assertArrayAlmostEqual(H_analytical, H_numerical, tol=0.03)
###

def test_symmetry(self):
        for calc in [{(1, 1): LennardJonesQuadratic(1, 1, 3), (1, 2): LennardJonesQuadratic(1.5, 0.8, 2.4), (2, 2): LennardJonesQuadratic(0.5, 0.88, 2.64)}]:
            a = io.read('KA256_Min.xyz')
            a.center(vacuum=5.0)
            b = calculator.PairPotential(calc)
            H = b.calculate_hessian_matrix(a, "dense")
            self.assertArrayAlmostEqual(np.sum(np.abs(H-H.T)), 0, tol=0)

def test_forces(self):
        for calc in [PairPotential({(1, 1): LennardJonesQuadratic(1, 1, 3), (1, 2): LennardJonesQuadratic(1.5, 0.8, 2.4), (2, 2): LennardJonesQuadratic(0.5, 0.88, 2.64)})]:
            a = io.read('KA256.xyz')
            a.center(vacuum=5.0)
            a.set_calculator(calc)
            f = a.get_forces()
            fn = calc.calculate_numerical_forces(a, d=0.0001)
            self.assertArrayAlmostEqual(f, fn, tol=self.tol)