How to use the kymatio.scattering2d.backend.cdgmm function in kymatio

order2_size = self.L ** 2 * J * (J - 1) // 2
        output_size = order0_size + order1_size

        if self.max_order == 2:
            output_size += order2_size

        S = input.new(input.size(0),
                      input.size(1),
                      output_size,
                      self.M_padded//(2**J)-2,
                      self.N_padded//(2**J)-2)
        U_r = pad(input)
        U_0_c = fft(U_r, 'C2C')  # We trick here with U_r and U_2_c

        # First low pass filter
        U_1_c = subsample_fourier(cdgmm(U_0_c, phi[0]), k=2**J)

        U_J_r = fft(U_1_c, 'C2R')

        S[..., 0, :, :] = unpad(U_J_r)
        n_order1 = 1
        n_order2 = 1 + order1_size

        for n1 in range(len(psi)):
            j1 = psi[n1]['j']
            U_1_c = cdgmm(U_0_c, psi[n1][0])
            if(j1 > 0):
                U_1_c = subsample_fourier(U_1_c, k=2 ** j1)
            U_1_c = fft(U_1_c, 'C2C', inverse=True)
            U_1_c = fft(modulus(U_1_c), 'C2C')

            # Second low pass filter

if(j1 > 0):
                U_1_c = subsample_fourier(U_1_c, k=2 ** j1)
            U_1_c = fft(U_1_c, 'C2C', inverse=True)
            U_1_c = fft(modulus(U_1_c), 'C2C')

            # Second low pass filter
            U_2_c = subsample_fourier(cdgmm(U_1_c, phi[j1]), k=2**(J-j1))
            U_J_r = fft(U_2_c, 'C2R')
            S[..., n_order1, :, :] = unpad(U_J_r)
            n_order1 += 1

            if self.max_order == 2:
                for n2 in range(len(psi)):
                    j2 = psi[n2]['j']
                    if(j1 < j2):
                        U_2_c = subsample_fourier(cdgmm(U_1_c, psi[n2][j1]), k=2 ** (j2-j1))
                        U_2_c = fft(U_2_c, 'C2C', inverse=True)
                        U_2_c = fft(modulus(U_2_c), 'C2C')

                        # Third low pass filter
                        U_2_c = subsample_fourier(cdgmm(U_2_c, phi[j2]), k=2 ** (J-j2))
                        U_J_r = fft(U_2_c, 'C2R')

                        S[..., n_order2, :, :] = unpad(U_J_r)
                        n_order2 += 1

        scattering_shape = S.shape[-3:]
        S = S.reshape(batch_shape + scattering_shape)

        return S

# Second low pass filter
            U_2_c = subsample_fourier(cdgmm(U_1_c, phi[j1]), k=2**(J-j1))
            U_J_r = fft(U_2_c, 'C2R')
            S[..., n_order1, :, :] = unpad(U_J_r)
            n_order1 += 1

            if self.max_order == 2:
                for n2 in range(len(psi)):
                    j2 = psi[n2]['j']
                    if(j1 < j2):
                        U_2_c = subsample_fourier(cdgmm(U_1_c, psi[n2][j1]), k=2 ** (j2-j1))
                        U_2_c = fft(U_2_c, 'C2C', inverse=True)
                        U_2_c = fft(modulus(U_2_c), 'C2C')

                        # Third low pass filter
                        U_2_c = subsample_fourier(cdgmm(U_2_c, phi[j2]), k=2 ** (J-j2))
                        U_J_r = fft(U_2_c, 'C2R')

                        S[..., n_order2, :, :] = unpad(U_J_r)
                        n_order2 += 1

        scattering_shape = S.shape[-3:]
        S = S.reshape(batch_shape + scattering_shape)

        return S

self.N_padded//(2**J)-2)
        U_r = pad(input)
        U_0_c = fft(U_r, 'C2C')  # We trick here with U_r and U_2_c

        # First low pass filter
        U_1_c = subsample_fourier(cdgmm(U_0_c, phi[0]), k=2**J)

        U_J_r = fft(U_1_c, 'C2R')

        S[..., 0, :, :] = unpad(U_J_r)
        n_order1 = 1
        n_order2 = 1 + order1_size

        for n1 in range(len(psi)):
            j1 = psi[n1]['j']
            U_1_c = cdgmm(U_0_c, psi[n1][0])
            if(j1 > 0):
                U_1_c = subsample_fourier(U_1_c, k=2 ** j1)
            U_1_c = fft(U_1_c, 'C2C', inverse=True)
            U_1_c = fft(modulus(U_1_c), 'C2C')

            # Second low pass filter
            U_2_c = subsample_fourier(cdgmm(U_1_c, phi[j1]), k=2**(J-j1))
            U_J_r = fft(U_2_c, 'C2R')
            S[..., n_order1, :, :] = unpad(U_J_r)
            n_order1 += 1

            if self.max_order == 2:
                for n2 in range(len(psi)):
                    j2 = psi[n2]['j']
                    if(j1 < j2):
                        U_2_c = subsample_fourier(cdgmm(U_1_c, psi[n2][j1]), k=2 ** (j2-j1))