code: public static DecryptionTool get(Key<DecryptionTool> key) {
      if (key == null)
        return new NullDecryptionTool();
      DecryptionTool decrypt = DKV.getGet(key);
      return decrypt == null ? new NullDecryptionTool() : decrypt;
    }
docs: Retrieves a Decryption Tool from DKV using a given key.
  @param key a valid DKV key or null
  @return instance of Decryption Tool for a valid key, Null Decryption tool for a null key