def _genCounterCallbacks(self):
        raise NotImplementedError()
:param postreader: the PostingReader object to read from.
dataset/ETHPy150Open facebook/sparts/sparts/sparts.py/ProvidesCounters._genCounterCallbacks--crossover with--dataset/ETHPy150Open dokipen/whoosh/src/whoosh/postings.py/Exclude.__init__