docs: public void disposeInstanceOf(Class<?> clazz, Object key, boolean keepPersistent)
           throws InvalidCacheUsageException {
  
        ContainerSignature signature = new ContainerSignature(clazz,key);
        if (log.isDebugEnabled()) log.debugf("Disposing %s",signature.toString());
        Container container;
        synchronized (registeredContainers) {
           container = registeredContainers.get(signature);
           if( container == null )
              return;
           if( ! container.getClazz().equals(clazz) )
              throw new InvalidCacheUsageException("The object is not of the right class.");
           registeredContainers.remove(signature);
        }
  
        try {
           container.dispose(keepPersistent);
        } catch (Exception e) {
           e.printStackTrace();
           throw new InvalidCacheUsageException("Error while disposing object " + key);
        }
  
     }