def __init__(self, initlist=[]):
        self.values = []
        self.keys = []
        for idx, item in enumerate(initlist):
            try:
                key, value = item
                key = None if key == '' else key
            except (TypeError, ValueError):
                value = item
                key = None
            finally:
                self.values.append(value)
                self.keys.append(key)
Items in initlist can either be
dataset/ETHPy150Open ralhei/pyRserve/pyRserve/taggedContainers.py/TaggedList.__init__