<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_update(self, user, **data):
 """ Sys admins can always update an organisation. Organisation admins and creators can update, but may not update the following fields: - star_rating :param user: a User :param data: data that the user wants to update :returns: bool, set of fields that the user was not authorized to update """

        if user.is_admin():
            raise Return((True, set([])))

        org_admin = user.is_org_admin(self.id)
        creator = self.created_by == user.id
        if org_admin or creator:
            fields = {'star_rating'} & set(data.keys())
            if fields:
                raise Return((False, fields))
            else:
                raise Return((True, set([])))

        raise Return((False, set([])))