'query method for custom placeholders list
:param view_kwargs:
:return:'

def query(self, view_kwargs):

    query_ = self.session.query(CustomPlaceholder)
    if view_kwargs.get('event_sub_topic_id'):
        event_sub_topic = safe_query(self, EventSubTopic, 'id', view_kwargs['event_sub_topic_id'], 'event_sub_topic_id')
        query_ = query_.join(EventSubTopic).filter((EventSubTopic.id == event_sub_topic.id))
    return query_
