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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 trajectory_SgConst(Sg=0.1, delta_logt_dex=-0.01):
    '''
    setup trajectories for constant radiation entropy.

    S_gamma/R where the radiation constant R = N_A*k
    (Dave Arnett, Supernova book, p. 212)
    This relates rho and T but the time scale for this
    is independent.

    Parameters
    ----------
    Sg : float
        S_gamma/R, values between 0.1 and 10. reflect conditions in
        massive stars.  The default is 0.1.
    delta_logt_dex : float
        Sets interval between time steps in dex of logtimerev.  The
        default is -0.01.

    '''

    # reverse logarithmic time
    logtimerev=np.arange(5.,-6.,delta_logt_dex)
    logrho=np.linspace(0,8.5,len(logtimerev))
    logT = (old_div(1.,3.))*(logrho + 21.9161 + np.log10(Sg))

    #rho_6=10**logrho/(0.1213*1.e6)
    #T9=rho_6**(1./3.)
    #logT_T3=np.log10(T9*1.e9)


    pl.close(3);pl.figure(3);pl.plot(logrho,logT,label='$S/\mathrm{N_Ak}='+str(Sg)+'$')
    pl.legend(loc=2);pl.xlabel('$\log \\rho$'); pl.ylabel('$\log T$')
    pl.close(5);pl.figure(5);pl.plot(logtimerev, logrho)
    pl.xlabel('$\log (t_\mathrm{final}-t)$'); pl.ylabel('$\log \\rho$')
    pl.xlim(8,-6)

    pl.close(6);pl.figure(6);pl.plot(logtimerev)
    pl.ylabel('$\log (t_\mathrm{final}-t)$'); pl.xlabel('cycle')

    # [t] logtimerev yrs
    # [rho] cgs
    # [T]   K

    T9=old_div(10**logT,1.e9)
    data=[logtimerev,T9,logrho]
    att.writeTraj(filename='trajectory.input', data=data, ageunit=2, tunit=1, rhounit=1, idNum=1)