public static <N> ImmutableGraph<N> emptyGraph(Graph<N> graph) {
        return ImmutableGraph.copyOf(GraphBuilder.from(graph).build());
    }
@Test
    public void emptyGraphWithTemplate() {
        final MutableGraph<String> templateGraph = GraphBuilder
                .directed()
                .allowsSelfLoops(true)
                .build();
        final ImmutableGraph<String> emptyGraph = Graphs.emptyGraph(templateGraph);
        assertThat(emptyGraph.isDirected()).isTrue();
        assertThat(emptyGraph.allowsSelfLoops()).isTrue();
        assertThat(emptyGraph.edges()).isEmpty();
        assertThat(emptyGraph.edges()).isEmpty();
    }