2     0.0         1355240               0  Int64
   8 │ uid             2840.84    4            531.0       15699             35744  Union{Missing, Int64}
   9 │ iso2                       AD                       ZW                49148  Union{Missing, String3}
  10 │ iso3                       ABW                      ZWE               45797  Union{Missing, String3}
  11 │ code3           375.042    4            336.0       894               45797  Union{Missing, Int64}
  12 │ combined_key      