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.
try {
      successors.add(N2);
      fail(ERROR_MODIFIABLE_COLLECTION);
    } catch (UnsupportedOperationException e) {
      addEdge(N1, N2, E12);
      assertThat(successors).containsExactlyElementsIn(network.successors(N1));
    }
  }
  @Test
  public void edges_containsOrderMismatch() {
    addEdge(N1, N2, E12);
    EndpointPair<Integer> endpointsN1N2 = EndpointPair.unordered(N1, N2);
    EndpointPair<Integer> endpointsN2N1 = EndpointPair.unordered(N2, N1);
    assertThat(network.asGraph().edges()).doesNotContain(endpointsN1N2);
    assertThat(network.asGraph().edges()).doesNotContain(endpointsN2N1);
  }
  @Test
  public void edgesConnecting_orderMismatch() {
    addEdge(N1, N2, E12);
    try {
      Set<String> unused = network.edgesConnecting(EndpointPair.unordered(N1, N2));
      fail("Expected IllegalArgumentException: " + ENDPOINTS_MISMATCH);
    } catch (IllegalArgumentException e) {
      assertThat(e).hasMessageThat().contains(ENDPOINTS_MISMATCH);
    }
  }
  @Test
  public void edgeConnectingOrNull_orderMismatch() {
    addEdge(N1, N2, E12);
    try {