code: public void addUserJarBlobKey(PermanentBlobKey key) {
  		if (key == null) {
  			throw new IllegalArgumentException();
  		}
  
  		if (!userJarBlobKeys.contains(key)) {
  			userJarBlobKeys.add(key);
  		}
  	}
docs: Adds the BLOB referenced by the key to the JobGraph's dependencies.
  
  @param key
  path of the JAR file required to run the job on a task manager