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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 downloadSessionImages(server, filename=None, height=150, width=150, opacity=100, saturation=100):
 # pragma: no cover """ Helper to download a bif image or thumb.url from plex.server.sessions. Parameters: filename (str):
 default to None, height (int):
 Height of the image. width (int):
 width of the image. opacity (int):
 Opacity of the resulting image (possibly deprecated). saturation (int):
 Saturating of the resulting image. Returns: {'hellowlol': {'filepath': '<filepath>', 'url': 'http://<url>'}, """

    info = {}
    for media in server.sessions():
        url = None
        for part in media.iterParts():
            if media.thumb:
                url = media.thumb
            if part.indexes:  # always use bif images if available.
                url = '/library/parts/%s/indexes/%s/%s' % (part.id, part.indexes.lower(), media.viewOffset)
        if url:
            if filename is None:
                prettyname = media._prettyfilename()
                filename = 'session_transcode_%s_%s_%s' % (media.usernames[0], prettyname, int(time.time()))
            url = server.transcodeImage(url, height, width, opacity, saturation)
            filepath = download(url, filename=filename)
            info['username'] = {'filepath': filepath, 'url': url}
    return info