'Should return a dict like:
result = {<season number>:
{1: \'<url 1>\', 2: <url 2>, ...},}'

def _season_banners_dict(self, show_obj, season):

    result = {}
    indexer_lang = show_obj.lang
    try:
        lINDEXER_API_PARMS = sickbeard.indexerApi(show_obj.indexer).api_params.copy()
        lINDEXER_API_PARMS[u'banners'] = True
        lINDEXER_API_PARMS[u'language'] = (indexer_lang or sickbeard.INDEXER_DEFAULT_LANGUAGE)
        t = sickbeard.indexerApi(show_obj.indexer).indexer(**lINDEXER_API_PARMS)
        indexer_show_obj = t[show_obj.indexerid]
    except (sickbeard.indexer_error, IOError) as e:
        logger.log((((u'Unable    to    look    up    show    on    ' + sickbeard.indexerApi(show_obj.indexer).name) + u',    not    downloading    images:    ') + ex(e)), logger.WARNING)
        logger.log(u'{0}    may    be    experiencing    some    problems.    Try    again    later.'.format(sickbeard.indexerApi(show_obj.indexer).name), logger.DEBUG)
        return result
    if (not getattr(indexer_show_obj, u'_banners', None)):
        return result
    if ((u'season' not in indexer_show_obj[u'_banners']) or (u'seasonwide' not in indexer_show_obj[u'_banners'][u'season'])):
        return result
    seasonsArtObj = indexer_show_obj[u'_banners'][u'season'][u'seasonwide']
    result[season] = {}
    for seasonArtID in seasonsArtObj.keys():
        if ((int(seasonsArtObj[seasonArtID][u'season']) == season) and (seasonsArtObj[seasonArtID][u'language'] == (indexer_lang or sickbeard.INDEXER_DEFAULT_LANGUAGE))):
            result[season][seasonArtID] = seasonsArtObj[seasonArtID][u'_bannerpath']
    return result
