def has_key(self, key):
        raise NotImplementedError('Method must be implemented by subclass')
Performs second degree crawling from the 1st crawl function. No recursion
dataset/ETHPy150Open babble/babble/include/jython/Lib/mailbox.py/Mailbox.has_key--crossover with--dataset/ETHPy150Open miklevin/pipulate/common.py/crawl