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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _use_memcache(self, key, options=None):
 """Return whether to use memcache for this key. Args: key: Key instance. options: ContextOptions instance, or None. Returns: True if the key should be cached in memcache, False otherwise. """

    flag = ContextOptions.use_memcache(options)
    if flag is None:
      flag = self._memcache_policy(key)
    if flag is None:
      flag = ContextOptions.use_memcache(self._conn.config)
    if flag is None:
      flag = True
    return flag