function _getRarity(string original, uint8 low, uint8 high) pure private returns (uint8) {
        uint32 rarity = stringToUint32(substring(original,low,high));
        if (rarity >= 950) {
          return GOLD; 
        } else if (rarity >= 850) {
          return SHADOW;
        } else {
          return STANDARD; 
        }
    }