docs: public void saveNow() throws IOException {
          // Can be called by any thread. However the wallet is locked whilst saving, so we can have two saves in flight
          // but they will serialize (using different temp files).
          if (executor.isShutdown())
              return;
          Date lastBlockSeenTime = wallet.getLastBlockSeenTime();
          log.info("Saving wallet; last seen block is height {}, date {}, hash {}", wallet.getLastBlockSeenHeight(),
                  lastBlockSeenTime != null ? Utils.dateTimeFormat(lastBlockSeenTime) : "unknown",
                  wallet.getLastBlockSeenHash());
          saveNowInternal();
      }