code: public <T> ServiceGraphModule registerForSpecificKey(Key<T> key, ServiceAdapter<T> factory) {
  		keys.put(key, factory);
  		return this;
  	}
docs: Puts the key and its factory to the keys
  
  @param key     key with which the specified factory is to be associated
  @param factory value to be associated with the specified key
  @param <T>     type of service
  @return ServiceGraphModule with change