@staticmethod<EOL><INDENT>def default_cache_policy(key):<DEDENT>
flag = None<EOL>if key is not None:<EOL><INDENT>modelclass = model.Model._kind_map.get(key.kind())<EOL>if modelclass is not None:<EOL><INDENT>policy = getattr(modelclass, '<STR_LIT>', None)<EOL>if policy is not None:<EOL><INDENT>if isinstance(policy, bool):<EOL><INDENT>flag = policy<EOL><DEDENT>else:<EOL><INDENT>flag = policy(key)<EOL><DEDENT><DEDENT><DEDENT><DEDENT>return flag<EOL>
Default cache policy.

        This defers to _use_cache on the Model class.

        Args:
          key: Key instance.

        Returns:
          A bool or None.