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.
assume().that(graphIsMutable()).isTrue();
    addNode(N1);
    addNode(N2);
    Set<String> edgesConnecting = network.edgesConnecting(N1, N2);
    try {
      edgesConnecting.add(E23);
      fail(ERROR_MODIFIABLE_COLLECTION);
    } catch (UnsupportedOperationException e) {
      addEdge(N1, N2, E12);
      assertThat(network.edgesConnecting(N1, N2)).containsExactlyElementsIn(edgesConnecting);
    }
  }
  @Override
  @Test
  public void inEdges_checkReturnedSetMutability() {
    assume().that(graphIsMutable()).isTrue();
    addNode(N2);
    Set<String> inEdges = network.inEdges(N2);
    try {
      inEdges.add(E12);
      fail(ERROR_MODIFIABLE_COLLECTION);
    } catch (UnsupportedOperationException e) {
      addEdge(N1, N2, E12);
      assertThat(network.inEdges(N2)).containsExactlyElementsIn(inEdges);
    }
  }
  @Override
  @Test
  public void outEdges_checkReturnedSetMutability() {
    assume().that(graphIsMutable()).isTrue();