class Holidays::Definition::Generator::Regions

def generate_parent_lookup(regions)
  lookup = {}
  regions.each do |region, subregions|
    subregions.each do |subregion|
      parent_region = NORTH_AMERICA_REGIONS.include?(subregion) ? subregion : region
      lookup[subregion] = parent_region unless lookup.has_key?(subregion)
    end
  end
  pairs = lookup.map { |k, v| "#{k}: :#{v}" }.join(", ")
  "{#{pairs}}"
end