def iterkeys(self):
        raise NotImplementedError('Method must be implemented by subclass')
Quote a header value if necessary.
dataset/ETHPy150Open babble/babble/include/jython/Lib/mailbox.py/Mailbox.iterkeys--crossover with--dataset/ETHPy150Open Eforcers/gae-flask-todo/lib/werkzeug/http.py/quote_header_value