During some minimization efforts on the previous released version 28.2-jre, I noticed a spurious file in the published version on maven central:

```
tn@proteus:~/Downloads$ unzip -l guava-28.2-jre.jar  | grep swp
    16384  2019-09-18 17:29   com/google/common/collect/.ImmutableListMultimap.java.swp
```

Looks like an transient artefact from an editor that slipped into the release. It is not present in the android variant or in older releases (I checked at least 28.1-jre).

Minor things that can not be changed anymore but maybe a trigger for improvement of future releases.

Edit: I noticed that 29.0 has been released that does not contain this spurious file.
public void validateSourceAndTarget() {
    for (Integer node : network.nodes()) {
      for (String inEdge : network.inEdges(node)) {
        EndpointPair<Integer> endpointPair = network.incidentNodes(inEdge);
        assertThat(endpointPair.source()).isEqualTo(endpointPair.adjacentNode(node));
        assertThat(endpointPair.target()).isEqualTo(node);
      }
      for (String outEdge : network.outEdges(node)) {
        EndpointPair<Integer> endpointPair = network.incidentNodes(outEdge);
        assertThat(endpointPair.source()).isEqualTo(node);
        assertThat(endpointPair.target()).isEqualTo(endpointPair.adjacentNode(node));
      }
      for (Integer adjacentNode : network.adjacentNodes(node)) {
        Set<String> edges = network.edgesConnecting(node, adjacentNode);
        Set<String> antiParallelEdges = network.edgesConnecting(adjacentNode, node);
        assertThat(node.equals(adjacentNode) || Collections.disjoint(edges, antiParallelEdges))
            .isTrue();
      }
    }
  }
  @Override
  @Test
  public void nodes_checkReturnedSetMutability() {
    assume().that(graphIsMutable()).isTrue();
    Set<Integer> nodes = network.nodes();
    try {
      nodes.add(N2);
      fail(ERROR_MODIFIABLE_COLLECTION);
    } catch (UnsupportedOperationException e) {
      addNode(N1);