def read_chunk(f, start, count):
    """ move around inside gigantor file and return the gzip'd embed """
    #print("read_chunk start,count= ",start,count)
    f.seek(start+256)  # offset plus header   ## SKIP: nothing of value in header?
    chunk = BytesIO(f.read(count-256))
    return gzip.GzipFile(fileobj=chunk)
 move around inside gigantor file and return the gzip'd embed 
Tools/ArcSight-Data-Migration/lacat-opt.py