code: public void printPathTo(long targetId) {
  		System.out.println(getPath(targetId).stream().map(String::valueOf).reduce((s1, s2) -> s1 + " -> " + s2).get());
  	}
docs: Prints the path between a source node and a target node, if it exists. If it does not exist, a message indicating this is shown.
  Is a path does exist, a sequence of nodes is printed to show the path that the nodes share.
  
  @param targetId the id of the target node in the graph.