'Create a staging scan request queue.
"maxsize" (optional) is an upperbound limit on the number of
items in the queue (<= 0 means the queue is unbounded).
"stagingDelay" (optional) is a number of seconds to use as a
delay from being staged to being placed on the queue.'

def __init__(self, maxsize=0, stagingDelay=None):

    _UniqueRequestPriorityQueue.__init__(self, maxsize)
    if (stagingDelay is None):
        self._stagingDelay = self.DEFAULT_STAGING_DELAY
    else:
        self._stagingDelay = stagingDelay
    self._onDeck = {}
    self._nothingOnDeck = threading.Lock()
    self._nothingOnDeck.acquire()
    self._terminate = 0
    self._stager = threading.Thread(target=self._stagingThread, name='request    staging    thread')
    self._stager.setDaemon(True)
    self._stager.start()
