src/main/java/org/jinstagram/realtime/InstagramSubscription.java
public InstagramSubscription callback(String callback) {
		Preconditions.checkValidUrl(callback, "Invalid Callback Url");

		this.params.put(Constants.CALLBACK_URL, callback);

		return this;
	}
public InstagramSubscription callback(String callback) {
		Preconditions.checkValidUrl(callback, "Invalid Callback Url");

		this.params.put(Constants.CALLBACK_URL, callback);

		return this;
	}
Configures the callback url

@param callback The callback for your application
@return the {@link InstagramSubscription} instance for method chaining