return ImmutableGraph.copyOf(graph);
  }

  private static void assertEqualCharNodes(Iterable<Character> result, String expectedCharacters) {
    assertThat(ImmutableList.copyOf(result))
        .containsExactlyElementsIn(Chars.asList(expectedCharacters.toCharArray()))
        .inOrder();
  }

  private static class RequestSavingGraph implements SuccessorsFunction<Character> {

    return ImmutableGraph.copyOf(graph);
  }

  private static void assertEqualCharNodes(Iterable<Character> result, String expectedCharacters) {
    assertThat(ImmutableList.copyOf(result))
        .containsExactlyElementsIn(Chars.asList(expectedCharacters.toCharArray()))
        .inOrder();
  }

  private static class RequestSavingGraph implements SuccessorsFunction<Character> {

                  }
                });
        assertWithMessage("Sets.combinations(%s, %s)", sampleSet, k)
            .that(Sets.combinations(sampleSet, k))
            .containsExactlyElementsIn(expected)
            .inOrder();
      }
    }
  }

  private static <E> Set<E> set(E... elements) {
    return ImmutableSet.copyOf(elements);
  }