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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 mark_broker_action_done(action, rid=None, unit=None):
 """Mark action as having been completed. @param action: name of action to be performed @returns None """

    rdata = relation_get(rid, unit) or {}
    broker_rsp = rdata.get(get_broker_rsp_key())
    if not broker_rsp:
        return

    rsp = CephBrokerRsp(broker_rsp)
    unit_name = local_unit().partition('/')[2]
    key = "unit_{}_ceph_broker_action.{}".format(unit_name, action)
    kvstore = kv()
    kvstore.set(key=key, value=rsp.request_id)
    kvstore.flush()