Set<N> nodes();

  /** Returns all edges in this graph. */
  Set<EndpointPair<N>> edges();

  //
  // Graph properties
  //

  /**
   * Returns true if the edges in this graph are directed. Directed edges connect a {@link
   * EndpointPair#source() source node} to a {@link EndpointPair#target() target node}, while
   * undirected edges connect a pair of nodes to each other.
   */
  boolean isDirected();

  Set<N> nodes();

  /** Returns all edges in this graph. */
  Set<EndpointPair<N>> edges();

  //
  // Graph properties
  //

  /**
   * Returns true if the edges in this graph are directed. Directed edges connect a {@link
   * EndpointPair#source() source node} to a {@link EndpointPair#target() target node}, while
   * undirected edges connect a pair of nodes to each other.
   */
  boolean isDirected();

  Set<N> predecessors();

  Set<N> successors();

  Set<E> incidentEdges();

  Set<E> inEdges();

  Set<E> outEdges();

  /**
   * Returns the set of edges connecting the origin node to {@code node}. For networks without
   * parallel edges, this set cannot be of size greater than one.
   */
  Set<E> edgesConnecting(N node);

  /**
   * Returns the node that is adjacent to the origin node along {@code edge}.
   *

      return false;
    }
    Graph<?> other = (Graph<?>) obj;

    return isDirected() == other.isDirected()
        && nodes().equals(other.nodes())
        && edges().equals(other.edges());
  }

  @Override
  public final int hashCode() {
    return edges().hashCode();
  }

  /** Returns a string representation of this graph. */
  @Override
  public String toString() {
    return "isDirected: "

      // Number of edges remaining is unknown (node's incident edges have been removed).
      AbstractGraphTest.validateGraph(graph);

      for (int i = numNodesToRemove; i < NUM_NODES; ++i) {
        assertThat(graph.removeNode(nodeList.get(i))).isTrue();
      }

      assertThat(graph.nodes()).isEmpty();
      assertThat(graph.edges()).isEmpty(); // no edges can remain if there's no nodes

        && network.allowsParallelEdges()
        && network.edges().size() > network.asGraph().edges().size()) {
      return true;
    }
    return hasCycle(network.asGraph());
  }

  /**
   * Performs a traversal of the nodes reachable from {@code node}. If we ever reach a node we've
   * already visited (following only outgoing edges and without reusing edges), we know there's a
   * cycle in the graph.
   */

 *   <li>graphs that do/don't allow self-loops
 *   <li>graphs whose nodes/edges are insertion-ordered, sorted, or unordered
 *   <li>graphs whose edges have associated values
 * </ul>
 *
 * <p>{@code ValueGraph}, as a subtype of {@code Graph}, explicitly does not support parallel edges,
 * and forbids implementations or extensions with parallel edges. If you need parallel edges, use

    ImmutableSet<String> edges = ImmutableSet.copyOf(network.edges());
    assertThat(networkAsMutableNetwork.addEdge(N1, N2, E12)).isFalse();
    assertThat(network.edges()).containsExactlyElementsIn(edges);
    assertThat(networkAsMutableNetwork.addEdge(N2, N1, E12)).isFalse();
    assertThat(network.edges()).containsExactlyElementsIn(edges);
  }

  @Test

        && network.allowsParallelEdges()
        && network.edges().size() > network.asGraph().edges().size()) {
      return true;
    }
    return hasCycle(network.asGraph());
  }

  /**
   * Performs a traversal of the nodes reachable from {@code node}. If we ever reach a node we've
   * already visited (following only outgoing edges and without reusing edges), we know there's a
   * cycle in the graph.
   */

		g.removeVertex_locked(neighbor.(*namedVertex))
	}

	// remove edges from destination indexes for neighbors that dropped outbound edges
	for _, edge := range edgesToRemoveFromIndexes {
		g.removeEdgeFromDestinationIndex_locked(edge)
	}
}

// must be called under write lock
// deletes edges from a given vertex type to a specific vertex