private static Protos.Transaction.Pool getProtoPool(WalletTransaction wtx) {
   switch (wtx.getPool()) {
     case UNSPENT:
       return Protos.Transaction.Pool.UNSPENT;
     case SPENT:
       return Protos.Transaction.Pool.SPENT;
     case DEAD:
       return Protos.Transaction.Pool.DEAD;
     case PENDING:
       return Protos.Transaction.Pool.PENDING;
     default:
       throw new RuntimeException("Unreachable");
   }
 }