The principle is that the statement has to address that the Party membership has been invalid due to not participating the Party activities, not paying Party membership,etc.
Here is some examples for your reference:
http://bbs.wenxuecity.com/immigration/461626.html
http://bbs.wenxuecity.com/immigration/396051.html
http://bbs.wenxuecity.com/immigration/310040.html