Return a list of the images that are on the provider

def avail_images(call=None):
    '''
    Return a list of the images that are on the provider
    '''
    if call == 'action':
        raise SaltCloudSystemExit(
            'The avail_images function must be called with '
            '-f or --function, or with the --list-images option'
        )

    ret = {}
    conn = get_conn()

    for item in conn.list_images()['items']:
        image = {'id': item['id']}
        image.update(item['properties'])
        ret[image['name']] = image

    return ret