def exists(self, session_key):
        raise NotImplementedError
Format a list of traceback entry tuples for printing.
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.4/django/contrib/sessions/backends/base.py/SessionBase.exists--crossover with--dataset/ETHPy150Open babble/babble/include/jython/Lib/traceback.py/format_list