<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def can_publish(self):
 """ Return True if there is a draft version of the document that's ready to be published. """

        with self.published_context():
            published = self.one(
                Q._uid == self._uid,
                projection={'revision': True}
                )

        if not published:
            return True

        with self.draft_context():
            draft = self.one(Q._uid == self._uid, projection={'revision': True})

        return draft.revision > published.revision