@classmethod
def get_oauthlib_core(cls):
    """
        Cache and return `OAuthlibCore` instance so it will be created only on first request
        """
    if not hasattr(cls, '_oauthlib_core'):
        server = cls.get_server()
        core_class = cls.get_oauthlib_backend_class()
        cls._oauthlib_core = core_class(server)
    return cls._oauthlib_core
