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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 _get_description(string):
 """ Parse annotation to get nice description """

    ann = set()
    if not string:
        return "This cluster is inter-genic."
    for item in string:
        for db in item:
            ann = ann.union(set(item[db]))
    return "annotated as: %s ..." % ",".join(list(ann)[:3])