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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 sun_rise_set_transit_ephem(times, latitude, longitude, next_or_previous='next', altitude=0, pressure=101325, temperature=12, horizon='0:00'):
 """ Calculate the next sunrise and sunset times using the PyEphem package. Parameters time : pandas.DatetimeIndex Must be localized latitude : float Latitude in degrees, positive north of equator, negative to south longitude : float Longitude in degrees, positive east of prime meridian, negative to west next_or_previous : str 'next' or 'previous' sunrise and sunset relative to time altitude : float, default 0 distance above sea level in meters. pressure : int or float, optional, default 101325 air pressure in Pascals. temperature : int or float, optional, default 12 air temperature in degrees C. horizon : string, format +/-X:YY arc degrees:arc minutes from geometrical horizon for sunrise and sunset, e.g., horizon='+0:00' to use sun center crossing the geometrical horizon to define sunrise and sunset, horizon='-0:34' for when the sun's upper edge crosses the geometrical horizon Returns ------- pandas.DataFrame index is the same as input `time` argument columns are 'sunrise', 'sunset', and 'transit' See also -------- pyephem """


    try:
        import ephem
    except ImportError:
        raise ImportError('PyEphem must be installed')

    # times must be localized
    if times.tz:
        tzinfo = times.tz
    else:
        raise ValueError('times must be localized')

    obs, sun = _ephem_setup(latitude, longitude, altitude,
                            pressure, temperature, horizon)
    # create lists of sunrise and sunset time localized to time.tz
    if next_or_previous.lower() == 'next':
        rising = obs.next_rising
        setting = obs.next_setting
        transit = obs.next_transit
    elif next_or_previous.lower() == 'previous':
        rising = obs.previous_rising
        setting = obs.previous_setting
        transit = obs.previous_transit
    else:
        raise ValueError("next_or_previous must be either 'next' or" +
                         " 'previous'")

    sunrise = []
    sunset = []
    trans = []
    for thetime in times:
        thetime = thetime.to_pydatetime()
        # pyephem drops timezone when converting to its internal datetime
        # format, so handle timezone explicitly here
        obs.date = ephem.Date(thetime - thetime.utcoffset())
        sunrise.append(_ephem_to_timezone(rising(sun), tzinfo))
        sunset.append(_ephem_to_timezone(setting(sun), tzinfo))
        trans.append(_ephem_to_timezone(transit(sun), tzinfo))

    return pd.DataFrame(index=times, data={'sunrise': sunrise,
                                           'sunset': sunset,
                                           'transit': trans})