}

    public static class CycleDetectedException extends Exception {
        private final List<String> cycle;

        CycleDetectedException(String message, List<String> cycle) {
            super(message);
            this.cycle = cycle;
        }

        public List<String> getCycle() {
            return cycle;
        }

        @Override
        public String getMessage() {

        from.children.add(to);
        to.parents.add(from);
        List<String> cycle = findCycle(to);
        if (cycle != null) {
            // remove edge which introduced cycle
            removeEdge(from, to);
            throw new CycleDetectedException(
                    "Edge between '" + from.label + "' and '" + to.label + "' introduces to cycle in the graph", cycle);
        }
    }

    void removeEdge(Vertex from, Vertex to) {

  }

  public void testConcat_infiniteIterable() throws IOException {
    CharSource source = CharSource.wrap("abcd");
    Iterable<CharSource> cycle = Iterables.cycle(ImmutableList.of(source));
    CharSource concatenated = CharSource.concat(cycle);

    String expected = "abcdabcd";

    // read the first 8 chars manually, since there's no equivalent to ByteSource.slice

  }

  public void testConcat_infiniteIterable() throws IOException {
    ByteSource source = ByteSource.wrap(new byte[] {0, 1, 2, 3});
    Iterable<ByteSource> cycle = Iterables.cycle(ImmutableList.of(source));
    ByteSource concatenated = ByteSource.concat(cycle);

    byte[] expected = {0, 1, 2, 3, 0, 1, 2, 3};
    assertArrayEquals(expected, concatenated.slice(0, 8).read());
  }

    assertEquals(expected, actual);
  }

  // Far less exhaustive than the tests in IteratorsTest
  public void testCycle() {
    Iterable<String> cycle = Iterables.cycle("a", "b");

    int howManyChecked = 0;
    for (String string : cycle) {
      String expected = (howManyChecked % 2 == 0) ? "a" : "b";
      assertEquals(expected, string);
      if (howManyChecked++ == 5) {
        break;
      }

            if (parentData == null) {
                currentData = superData;
            } else if (!parentIds.add(parentData.id())) {
                StringBuilder message = new StringBuilder("The parents form a cycle: ");
                for (String parentId : parentIds) {
                    message.append(parentId).append(" -> ");
                }
                message.append(parentData.id());

          }

          @Override
          public void remove() {
            listIter.remove();
          }
        };
      }
    };
  }

  static <T extends @Nullable Object> Iterator<T> cycle(Iterable<T> iterable) {
    return new Iterator<T>() {
      Iterator<T> iterator = Collections.<T>emptySet().iterator();

      @Override
      public boolean hasNext() {
        return true;
      }

        List<String> cycle = cde.getCycle();
        assertNotNull(cycle, "Cycle should be not null");
        assertTrue(cycle.contains("a"), "Cycle contains 'a'");
        assertTrue(cycle.contains("b"), "Cycle contains 'b'");
        assertTrue(cycle.contains("c"), "Cycle contains 'c'");

        Graph graph3 = new Graph();
        addEdge(graph3, "a", "b");

     * -Djcifs.smb1.smb.client.soTimeout=35000<br>
     * -Djcifs.smb1.smb.client.responseTimeout=30000<br>
     * -Dio.netty.noUnsafe=true<br>
     * -Dio.netty.noKeySetOptimization=true<br>
     * -Dio.netty.recycler.maxCapacityPerThread=0<br>
     * -Dlog4j.shutdownHookEnabled=false<br>
     * -Dlog4j2.formatMsgNoLookups=true<br>
     * -Dlog4j2.disable.jmx=true<br>
     * -Dlog4j.skipJansi=true<br>

      assertTrue(cycle.hasNext());
      assertEquals("b", cycle.next());
    }
  }

  public void testCycleOfTwoWithRemove() {
    Iterable<String> iterable = Lists.newArrayList("a", "b");
    Iterator<String> cycle = Iterators.cycle(iterable);
    assertTrue(cycle.hasNext());
    assertEquals("a", cycle.next());
    assertTrue(cycle.hasNext());
    assertEquals("b", cycle.next());
    assertTrue(cycle.hasNext());