Serves an individual image.

def _serve_individual_image(self, request):
    """Serves an individual image."""
    run = request.args.get('run')
    tag = request.args.get('tag')
    index = int(request.args.get('index'))
    sample = int(request.args.get('sample', 0))
    data = self._get_individual_image(run, tag, index, sample)
    image_type = imghdr.what(None, data)
    content_type = _IMGHDR_TO_MIMETYPE.get(image_type, _DEFAULT_IMAGE_MIMETYPE)
    return http_util.Respond(request, data, content_type)