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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 unblock_username(username, pipe=None):
 """ unblock the given Username """

    do_commit = False
    if not pipe:
        pipe = REDIS_SERVER.pipeline()
        do_commit = True
    if username:
        pipe.delete(get_username_attempt_cache_key(username))
        pipe.delete(get_username_blocked_cache_key(username))
        if do_commit:
            pipe.execute()