*   tf.optimizers => tf.keras.optimizers
    *   Add tf.keras.layers.AbstractRNNCell as the preferred implementation of
        RNN cell for TF v2. User can use it to implement RNN cell with custom
        behavior.
    *   Adding `clear_losses` API to be able to clear losses at the end of
        forward pass in a custom training loop in eager.

			Optional:    true,
			Type:        "string",
		},
		config.HelpKV{
			Key:         ConfigURL,
			Description: `openid discovery document e.g. "https://accounts.google.com/.well-known/openid-configuration"` + defaultHelpPostfix(ConfigURL),
			Type:        "url",
		},
		config.HelpKV{
			Key:         ClientID,

            //
            // 2. not to cancel any Future the user returned from an AsyncCallable
            //
            // We promise this because, once we cancel that Future, we would no longer be able to
            // tell when any underlying work it is doing is done. Thus, we might start a new task
            // while that underlying work is still running.
            //
            // So that is why we cancel only in the case of CAS success.

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