}
    };
  }

  @Override
  @CheckForNull
  public N removeInEdge(E edge, boolean isSelfLoop) {
    if (!isSelfLoop) {
      return removeOutEdge(edge);
    }
    return null;
  }

  @Override
  public N removeOutEdge(E edge) {
    N node = super.removeOutEdge(edge);
    Multiset<N> adjacentNodes = getReference(adjacentNodesReference);
    if (adjacentNodes != null) {
      checkState(adjacentNodes.remove(node));

  }

  @Override
  @CheckForNull
  public N removeInEdge(E edge, boolean isSelfLoop) {
    if (!isSelfLoop) {
      return removeOutEdge(edge);
    }
    return null;
  }

  @Override
  public N removeOutEdge(E edge) {
    N previousNode = incidentEdgeMap.remove(edge);
    // We're relying on callers to call this method only with an edge that's in the graph.

    N previousNode = inEdgeMap.remove(edge);
    // We're relying on callers to call this method only with an edge that's in the graph.
    return requireNonNull(previousNode);
  }

  @Override
  public N removeOutEdge(E edge) {
    N previousNode = outEdgeMap.remove(edge);
    // We're relying on callers to call this method only with an edge that's in the graph.
    return requireNonNull(previousNode);
  }

  @Override

  @CanIgnoreReturnValue
  @CheckForNull
  N removeInEdge(E edge, boolean isSelfLoop);

  /** Remove {@code edge} from the set of outgoing edges. Returns the former successor node. */
  @CanIgnoreReturnValue
  N removeOutEdge(E edge);

  /**
   * Add {@code edge} to the set of incoming edges. Implicitly adds {@code node} as a predecessor.
   */
  void addInEdge(E edge, N node, boolean isSelfLoop);

    N previousNode = inEdgeMap.remove(edge);
    // We're relying on callers to call this method only with an edge that's in the graph.
    return requireNonNull(previousNode);
  }

  @Override
  public N removeOutEdge(E edge) {
    N previousNode = outEdgeMap.remove(edge);
    // We're relying on callers to call this method only with an edge that's in the graph.
    return requireNonNull(previousNode);
  }

  @Override

    N nodeV = connectionsU.adjacentNode(edge);
    NetworkConnections<N, E> connectionsV = requireNonNull(nodeConnections.get(nodeV));
    connectionsU.removeOutEdge(edge);
    connectionsV.removeInEdge(edge, allowsSelfLoops() && nodeU.equals(nodeV));
    edgeToReferenceNode.remove(edge);
    return true;
  }

  private NetworkConnections<N, E> newConnections() {