Sign Instance
GET /data/api/signs/234/?format=api
http://labasi.acdh.oeaw.ac.at/data/api/signs/234/?format=api", "sign_name": "AG", "abz_number": "97", "meszl_number": "127", "image_1": "http://labasi.acdh.oeaw.ac.at/media/sign_img/ag_97.jpg", "image_2": null }{ "url": "