Returns the ImageId to use

def get_imageid(vm_):
    '''
    Returns the ImageId to use
    '''
    image = config.get_cloud_config_value(
        'image', vm_, __opts__, search_global=False
    )
    if image.startswith('ami-'):
        return image
    # a poor man's cache
    if not hasattr(get_imageid, 'images'):
        get_imageid.images = {}
    elif image in get_imageid.images:
        return get_imageid.images[image]
    params = {'Action': 'DescribeImages',
              'Filter.0.Name': 'name',
              'Filter.0.Value.0': image}
    # Query AWS, sort by 'creationDate' and get the last imageId
    _t = lambda x: datetime.datetime.strptime(x['creationDate'], '%Y-%m-%dT%H:%M:%S.%fZ')
    image_id = sorted(aws.query(params, location=get_location(),
                                 provider=get_provider(), opts=__opts__, sigver='4'),
                      lambda i, j: salt.utils.compat.cmp(_t(i), _t(j))
                      )[-1]['imageId']
    get_imageid.images[image] = image_id
    return image_id