Did you modify the class before getting the IllegalAnnotationException? I had to work through one of those when I had added the simple date format as a class member variable. You shouldn't declare any additional variables in the automatically generated class, try to keep those variables all within the getParsedPoints method. If you use the API instead of poll to try importing the file, you can monitor status at the temporary resource location it provides you. Through the UI, you should be redirected to a page you could refresh by clicking...
Other than that, printing or throwing exceptions from your implementing class is the easiest way to get debug information. If you
throw new java.lang.RuntimeException("my message"); you'll get a stack trace to that part of your code in the log and in an event, or you can simply System.out.println() as I did, but you would need to be watching stdout