def async_keys(self, callback):
        self._schedule(self.store_keys_async, callback=callback)
Queries Google Compute Engine to see if the specified persistent disk
dataset/ETHPy150Open kivy/kivy/kivy/storage/__init__.py/AbstractStore.async_keys--crossover with--dataset/ETHPy150Open AppScale/appscale-tools/lib/agents/gce_agent.py/GCEAgent.does_disk_exist