'Returns an item\'s item-rating association class.'

def _get_item_rating_assoc_class(self, item, webapp_model=None):

    if (webapp_model is None):
        webapp_model = galaxy.model
    item_rating_assoc_class = ('%sRatingAssociation' % item.__class__.__name__)
    return getattr(webapp_model, item_rating_assoc_class, None)
