def ensure_cache_version
      return unless cache

      cache_version = cache[cache_key('version')]
      minimum_version = '0.4.0'
      if cache_version &&
         Gem::Version.new(cache_version) < Gem::Version.new(minimum_version)
        @data[:cache] = nil
        raise "OSRM API error: Incompatible cache version #{cache_version}, " +
              "expected #{minimum_version} or higher"
      end
    end
def ensure_cache_version
      return unless cache

      cache_version = cache[cache_key('version')]
      minimum_version = '0.4.0'
      if cache_version &&
         Gem::Version.new(cache_version) < Gem::Version.new(minimum_version)
        @data[:cache] = nil
        raise "OSRM API error: Incompatible cache version #{cache_version}, " +
              "expected #{minimum_version} or higher"
      end
    end
Raise an exception if the cache isn't compatible with the current library version