def _use_cache(self, key, options=None):
    flag = ContextOptions.use_cache(options)
    if flag is None:
      flag = self._cache_policy(key)
    if flag is None:
      flag = ContextOptions.use_cache(self._conn.config)
    if flag is None:
      flag = True
    return flag
Return whether to use the context cache for this key.
dataset/ETHPy150Open AppScale/appscale/AppServer/google/appengine/ext/ndb/context.py/Context._use_cache