/** Returns the children of the specified node. Must not contain null. */
  public abstract Iterable<T> children(T root);

  /**
   * Returns an unmodifiable iterable over the nodes in a tree structure, using pre-order traversal.
   * That is, each node's subtrees are traversed after the node itself is returned.
   *
   * <p>No guarantees are made about the behavior of the traversal when nodes change while iteration

![Swagger UI](https://fastapi.tiangolo.com/img/index/index-03-swagger-02.png)

* Click on the button "Try it out", it allows you to fill the parameters and directly interact with the API:

![Swagger UI interaction](https://fastapi.tiangolo.com/img/index/index-04-swagger-03.png)

    checkNotNull(nodeU);
    checkNotNull(nodeV);
    return nodes().contains(nodeU) && successors(nodeU).contains(nodeV);
  }

  @Override
  public boolean hasEdgeConnecting(EndpointPair<N> endpoints) {
    checkNotNull(endpoints);
    if (!isOrderingCompatible(endpoints)) {
      return false;
    }
    N nodeU = endpoints.nodeU();
    N nodeV = endpoints.nodeV();

    for (Integer node : graph.nodes()) {
      new EqualsTester()
          .addEqualityGroup(
              graph.predecessors(node), graph.successors(node), graph.adjacentNodes(node))
          .testEquals();
    }
  }

  @Override
  @Test
  public void nodes_checkReturnedSetMutability() {
    assume().that(graphIsMutable()).isTrue();

    Set<Integer> nodes = graph.nodes();

      @Override
      public Set<N> adjacentNodes(N node) {
        return AbstractValueGraph.this.adjacentNodes(node);
      }

      @Override
      public Set<N> predecessors(N node) {
        return AbstractValueGraph.this.predecessors(node);
      }

      @Override
      public Set<N> successors(N node) {
        return AbstractValueGraph.this.successors(node);
      }

      @Override

![Swagger UI](https://fastapi.tiangolo.com/img/index/index-03-swagger-02.png)

* Tẹ bọtini "Gbiyanju rẹ" i.e. "Try it out", yóò gbà ọ́ láàyè láti jẹ́ kí ó tẹ́ àlàyé tí ó nílò kí ó le sọ̀rọ̀ tààrà pẹ̀lú API:

![Swagger UI interaction](https://fastapi.tiangolo.com/img/index/index-04-swagger-03.png)

![Swagger UI](https://fastapi.tiangolo.com/img/index/index-03-swagger-02.png)

* روی دکمه "Try it out" کلیک کنید، اکنون می‌توانید پارامترهای مورد نیاز هر API را مشخص کرده و به صورت مستقیم با آنها تعامل کنید:

![Swagger UI interaction](https://fastapi.tiangolo.com/img/index/index-04-swagger-03.png)

  /** Returns the children of the specified node. Must not contain null. */
  public abstract Iterable<T> children(T root);

  /**
   * Returns an unmodifiable iterable over the nodes in a tree structure, using pre-order traversal.
   * That is, each node's subtrees are traversed after the node itself is returned.
   *
   * <p>No guarantees are made about the behavior of the traversal when nodes change while iteration

  @Override
  @Test
  public void nodes_checkReturnedSetMutability() {
    assume().that(graphIsMutable()).isTrue();

    Set<Integer> nodes = graph.nodes();
    assertThrows(UnsupportedOperationException.class, () -> nodes.add(N2));
    addNode(N1);
    assertThat(graph.nodes()).containsExactlyElementsIn(nodes);
  }

  @Override
  @Test
  public void adjacentNodes_checkReturnedSetMutability() {

        case ERROR_INVALID_STATE:
            return "Invalid state";
        default:
            return "Unknown error: 0x" + Integer.toHexString(returnCode);
        }
    }

    /**
     * Encodes the witness RPC message parameters to NDR format.
     * Subclasses must implement this method to encode their specific parameters.
     *
     * @param buf the NDR buffer to encode into