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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def solve(self, neigs=4, tol=0, guess=None, mode_profiles=True, initial_mode_guess=None):
 """ This function finds the eigenmodes. Parameters neigs : int number of eigenmodes to find tol : float Relative accuracy for eigenvalues. The default value of 0 implies machine precision. guess : float a guess for the refractive index. Only finds eigenvectors with an effective refractive index higher than this value. Returns ------- self : an instance of the VFDModeSolver class obtain the fields of interest for specific modes using, for example: solver = EMpy.modesolvers.FD.VFDModeSolver(wavelength, x, y, epsf, boundary).solve() Ex = solver.modes[0].Ex Ey = solver.modes[0].Ey Ez = solver.modes[0].Ez """


        from scipy.sparse.linalg import eigen

        self.nmodes = neigs
        self.tol = tol

        A = self.build_matrix()

        if guess is not None:
            # calculate shift for eigs function
            k = 2 * numpy.pi / self.wl
            shift = (guess * k) ** 2
        else:
            shift = None

        [eigvals, eigvecs] = eigen.eigs(A,
                                        k=neigs,
                                        which='LR',
                                        tol=0.001,
                                        ncv=None,
                                        v0 = initial_mode_guess,
                                        return_eigenvectors=mode_profiles,
                                        sigma=shift)

        neffs = self.wl * scipy.sqrt(eigvals) / (2 * numpy.pi)
        if mode_profiles:
            Hxs = []
            Hys = []
            nx = self.nx
            ny = self.ny
            for ieig in range(neigs):
                Hxs.append(eigvecs[:nx * ny, ieig].reshape(nx, ny))
                Hys.append(eigvecs[nx * ny:, ieig].reshape(nx, ny))

        # sort the modes
        idx = numpy.flipud(numpy.argsort(neffs))
        neffs = neffs[idx]
        self.neff = neffs
        if mode_profiles:
            tmpx = []
            tmpy = []
            for i in idx:
                tmpx.append(Hxs[i])
                tmpy.append(Hys[i])
            Hxs = tmpx
            Hys = tmpy

            [Hzs, Exs, Eys, Ezs] = self.compute_other_fields(neffs, Hxs, Hys)

            self.modes = []
            for (neff, Hx, Hy, Hz, Ex, Ey, Ez) in zip(neffs, Hxs, Hys, Hzs, Exs, Eys, Ezs):
                self.modes.append(
                    FDMode(self.wl, self.x, self.y, neff, Ey, Ex, Ez, Hy, Hx, Hz).normalize())

        return self