code: public Future<T> retrieve(String key) {
  		assert (key != null);
  		return cache.get(key);
  	}
docs: Returns directly the <code>Future</code> associated with the key or null
  if an entry does not exist. This method will not create a task for a
  non-existent entry. This method is primarily used for testing.
  
  @param key
  Key to use for the entity lookup.
  
  @return <code>Future</code> for the named template or null if it is not
  in the cache