@NullMarked
public class MultimapPutTester<K extends @Nullable Object, V extends @Nullable Object>
    extends AbstractMultimapTester<K, V, Multimap<K, V>> {
  @MapFeature.Require(absent = SUPPORTS_PUT)
  public void testPutUnsupported() {
    assertThrows(UnsupportedOperationException.class, () -> multimap().put(k3(), v3()));
  }

  @MapFeature.Require(SUPPORTS_PUT)
  public void testPutEmpty() {
    int size = getNumElements();