ISO 3166-2 codes

[wldevries]

The ISO 3166-2 code for Groningen is NL-GR. I'm not sure if that is the value that should be in state_code or whether it's not present at all. We work mainly with ISO 3166-2 codes and it would be great to look them up with this tool.

postal_code                                9625
country_code                                 NL
place_name                           Overschild
state_name                            Groningen
state_code                                    4
county_name       Midden-Groningen Municipality
county_code                              1952.0
community_name                              NaN
community_code                              NaN
latitude                                53.2777
longitude                                6.7812
accuracy                                    6.0