How to use the sgp4.propagation.sgp4init function in sgp4

sec_whole, sec_fraction = divmod(sec, 1.0)

    satrec.epochyr = year
    satrec.jdsatepoch = jday(year,mon,day,hr,minute,sec);
    try:
        satrec.epoch = datetime(year, mon, day, hr, minute, int(sec_whole),
                                int(sec_fraction * 1000000.0 // 1.0))
    except ValueError:
        # Sometimes a TLE says something like "2019 + 366.82137887 days"
        # which would be December 32nd which causes a ValueError.
        year, mon, day, hr, minute, sec = invjday(satrec.jdsatepoch)
        satrec.epoch = datetime(year, mon, day, hr, minute, int(sec_whole),
                                int(sec_fraction * 1000000.0 // 1.0))

    #  ---------------- initialize the orbit at sgp4epoch -------------------
    sgp4init(whichconst, opsmode, satrec.satnum, satrec.jdsatepoch-2433281.5, satrec.bstar,
             satrec.ndot, satrec.nddot, satrec.ecco, satrec.argpo, satrec.inclo, satrec.mo,
             satrec.no_kozai, satrec.nodeo, satrec)

    return satrec

def test_legacy_initialized_with_sgp4init():
    sat = model.Satellite()
    sgp4init(
        wgs72, 'i', VANGUARD_ATTRS['satnum'], VANGUARD_EPOCH,
        *sgp4init_args(VANGUARD_ATTRS) + (sat,)
    )
    verify_vanguard_1(sat, legacy=True)

#  ---- find standard orbital elements ----
    satrec.inclo = satrec.inclo  * deg2rad;
    satrec.nodeo = satrec.nodeo  * deg2rad;
    satrec.argpo = satrec.argpo  * deg2rad;
    satrec.mo    = satrec.mo     * deg2rad;

    satrec.alta = satrec.a*(1.0 + satrec.ecco) - 1.0;
    satrec.altp = satrec.a*(1.0 - satrec.ecco) - 1.0;

    satrec.epochyr = dt_obj.year
    satrec.jdsatepoch = epoch/86400.0 + 2440587.5
    satrec.epoch = dt_obj

    #  ---------------- initialize the orbit at sgp4epoch -------------------
    sgp4init(whichconst, afspc_mode, satrec.satnum, satrec.jdsatepoch-2433281.5, satrec.bstar,
             satrec.ecco, satrec.argpo, satrec.inclo, satrec.mo, satrec.no,
             satrec.nodeo, satrec)

    return satrec

#  ---- find standard orbital elements ----
    satrec.inclo = satrec.inclo  * deg2rad;
    satrec.nodeo = satrec.nodeo  * deg2rad;
    satrec.argpo = satrec.argpo  * deg2rad;
    satrec.mo    = satrec.mo     * deg2rad;

    satrec.alta = satrec.a*(1.0 + satrec.ecco) - 1.0;
    satrec.altp = satrec.a*(1.0 - satrec.ecco) - 1.0;

    satrec.epochyr = dt_obj.year
    satrec.jdsatepoch = epoch/86400.0 + 2440587.5
    satrec.epoch = dt_obj

    #  ---------------- initialize the orbit at sgp4epoch -------------------
    sgp4init(whichconst, afspc_mode, satrec.satnum, satrec.jdsatepoch-2433281.5, satrec.bstar,
             satrec.ecco, satrec.argpo, satrec.inclo, satrec.mo, satrec.no,
             satrec.nodeo, satrec)
             

    return satrec