def lut_init(lut_key = nil)
      if lut_key
        lut(lut_key)
      else
        lut_keys.each { |k| lut_init(k) }
      end

      lut_keys
    end
def lut_init(lut_key = nil)
      if lut_key
        lut(lut_key)
      else
        lut_keys.each { |k| lut_init(k) }
      end

      lut_keys
    end
Init complete LUT with all keys define.
 But won't rewrite cache if allready written!
 * Returns: Foobar.lut_keys
     Foobar.lut_init
     => [:id, :foo, :bar, :foobar]