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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 hash_opensubtitles(video_path):
 """Compute a hash using OpenSubtitles' algorithm. :param str video_path: path of the video. :return: the hash. :rtype: str """

    bytesize = struct.calcsize(b'<q')
    with open(video_path, 'rb') as f:
        filesize = os.path.getsize(video_path)
        filehash = filesize
        if filesize < 65536 * 2:
            return
        for _ in range(65536 // bytesize):
            filebuffer = f.read(bytesize)
            (l_value,) = struct.unpack(b'<q', filebuffer)
            filehash += l_value
            filehash &= 0xFFFFFFFFFFFFFFFF  # to remain as 64bit number
        f.seek(max(0, filesize - 65536), 0)
        for _ in range(65536 // bytesize):
            filebuffer = f.read(bytesize)
            (l_value,) = struct.unpack(b'<q', filebuffer)
            filehash += l_value
            filehash &= 0xFFFFFFFFFFFFFFFF
    returnedhash = '%016x' % filehash

    return returnedhash