Get severity of correlated alert. Used to determine previous severity.

def get_severity(self, alert):
        """
        Get severity of correlated alert. Used to determine previous severity.
        """
        query = {
            'environment': alert.environment,
            'resource': alert.resource,
            '$or': [
                {
                    'event': alert.event,
                    'severity': {'$ne': alert.severity}
                },
                {
                    'event': {'$ne': alert.event},
                    'correlate': alert.event
                }],
            'customer': alert.customer
        }
        r = self.get_db().alerts.find_one(query, projection={'severity': 1, '_id': 0})
        return r['severity'] if r else None