@Override
  public @Nullable V put(K key, V value) {
    return delegate.put(checkValid(key), value);
  }

  @Override
  public void putAll(Map<? extends K, ? extends V> map) {
    for (K key : map.keySet()) {
      checkValid(key);
    }
    delegate.putAll(map);
  }

  @Override
  public @Nullable V remove(Object key) {
    return delegate.remove(checkValid(key));
  }

  @Override

        Properties merged = new Properties();
        if (sourceDominant) {
            merged.putAll(target.getProperties());
            merged.putAll(source.getProperties());
        } else {
            merged.putAll(source.getProperties());
            merged.putAll(target.getProperties());
        }
        target.setProperties(merged);
        target.setLocation(
                "properties",

   */
  @CanIgnoreReturnValue
  boolean putAll(@ParametricNullness K key, Iterable<? extends V> values);

  /**
   * Stores all key-value pairs of {@code multimap} in this multimap, in the order returned by
   * {@code multimap.entries()}.
   *
   * @return {@code true} if the multimap changed
   */
  @CanIgnoreReturnValue
  boolean putAll(Multimap<? extends K, ? extends V> multimap);

  /**

 * implementation for the {@link #put} and {@link #getIfPresent} methods. {@link #getAllPresent} is
 * implemented in terms of {@link #getIfPresent}; {@link #putAll} is implemented in terms of {@link
 * #put}, {@link #invalidateAll(Iterable)} is implemented in terms of {@link #invalidate}. The
 * method {@link #cleanUp} is a no-op. All other methods throw an {@link

        fields.put(key, value);
    }

    @Override
    public Map<String, Object> toSource() {
        final Map<String, Object> sourceMap = super.toSource();
        if (fields != null) {
            sourceMap.putAll(fields);
        }
        return sourceMap;
    }

    @Override
    protected void addFieldToSource(final Map<String, Object> sourceMap, final String field, final Object value) {

        return systemProperties;
    }

    public MavenExecutionRequest getRequest() {
        return request;
    }

    public void setUserProperties(Properties properties) {
        this.userProperties.putAll(properties);
    }

    public Path getRootDirectory() {
        return rootDirectory;
    }

    public Path getTopDirectory() {
        return topDirectory;
    }

        transformValues(ImmutableMap.of("a", 1), Functions.toStringFunction());
    assertThrows(UnsupportedOperationException.class, () -> map.put("b", "2"));

    assertThrows(UnsupportedOperationException.class, () -> map.putAll(ImmutableMap.of("b", "2")));

    assertThrows(
        UnsupportedOperationException.class,
        () -> map.entrySet().iterator().next().setValue("one"));
  }

  public void testTransformRemoveEntry() {

                    ImmutableSetMultimap<String, Integer> badEntries =
                        ImmutableSetMultimap.of("foo", 314, "one", 159, "two", 265, "bar", 358);
                    multimap.putAll(badEntries);
                    return Multimaps.filterEntries(
                        multimap, not(Predicates.in(badEntries.entries())));
                  }
                })

        // ----------------------------------------------------------------------

        EnvironmentUtils.addEnvVars(systemProperties);
        SystemProperties.addSystemProperties(systemProperties);
        systemProperties.putAll(context.systemPropertiesOverrides);

        // ----------------------------------------------------------------------
        // Properties containing info about the currently running version of Maven

    List<V> valuesToPut = asList(v0(), v1(), v0());

    for (K k : sampleKeys()) {
      resetContainer();

      Set<V> expectedValues = copyToSet(multimap().get(k));

      multimap().putAll(k, valuesToPut);
      expectedValues.addAll(valuesToPut);

      assertGet(k, expectedValues);
    }
  }