findClosest method
Finds the GeoLocationNode (City, Region, or Country) instance closest to the provided target
Returns: A City when possible, otherwise a Region or a Country, whichever is more specific.
Implementation
GeoLocationNode? findClosest(GeoCoords target) {
final country = countries.findClosestTo(target);
if (country == null) return null;
return country.findClosest(target);
}