def __init__(self):
        self.elements = defaultdict(list)
        self.is_ordered = True
        self.priorities = []
        self.size = 0
        self._cached_elements = None
Returns an OrderedReceivers object that externaly behaves
dataset/ETHPy150Open ARM-software/workload-automation/wlauto/external/louie/prioritylist.py/PriorityList.__init__