pub const NON_REGION_CITY_PREFIX: u8 = b'_';Expand description
IanaToBcp47Map’s trie cannot handle differently-cased prefixes, like Mexico/BajaSur`` and MET`.
Therefore, any ID that is not of the shape {region}/{city} gets prefixed with this character
inside the trie.
During lookup, if the input is not of the shape {region}/{city}, the trie cursor has to be advanced over
this byte.