code: public void addVertex(final JobTaskVertex taskVertex) {
  
  		if (!taskVertices.containsKey(taskVertex.getID())) {
  			taskVertices.put(taskVertex.getID(), taskVertex);
  		}
  	}
docs: Adds a new task vertex to the job graph if it is not already included.
  
  @param taskVertex
  the new task vertex to be added