code: @Override
      public void unlock(final Object maintainer) throws CouldNotPerformException {
          synchronized (maintainerLock) {
              if (this.maintainer != null && this.maintainer != maintainer) {
                  throw new CouldNotPerformException("Could not unlock remote because it is locked by another instance!");
              }
              this.maintainer = null;
          }
      }
docs: Method unlocks this instance.
  
  @param maintainer the instance which currently holds the lock.
  
  @throws CouldNotPerformException is thrown if the instance could not be
  unlocked.