Function to process a JSON message delivered from Amazon

def process_message(message, notification):
    """
    Function to process a JSON message delivered from Amazon
    """
    # Confirm that there are 'notificationType' and 'mail' fields in our
    # message
    if not set(VITAL_MESSAGE_FIELDS) <= set(message):
        # At this point we're sure that it's Amazon sending the message
        # If we don't return a 200 status code, Amazon will attempt to send us
        # this same message a few seconds later.
        logger.info('JSON Message Missing Vital Fields')
        return HttpResponse('Missing Vital Fields')

    if message['notificationType'] == 'Complaint':
        return process_complaint(message, notification)
    if message['notificationType'] == 'Bounce':
        return process_bounce(message, notification)
    if message['notificationType'] == 'Delivery':
        return process_delivery(message, notification)
    else:
        return HttpResponse('Unknown Notification Type')