return (Collector) TO_OPTIONAL;
  }

  private static final Object NULL_PLACEHOLDER = new Object();

  private static final Collector<@Nullable Object, ?, @Nullable Object> ONLY_ELEMENT =
      Collector.<@Nullable Object, ToOptionalState<Object>, @Nullable Object>of(
          () -> new ToOptionalState<>(null),
          (state, o) -> state.add((o == null) ? NULL_PLACEHOLDER : o),

        final List<Map<String, Object>> list = List.of(Map.of("id", "1"), Map.of("id", "2"));
        final Map<String, Object> map = Map.of("items", list);
        final List<Map<String, Object>> result = coordinatorHelper.getListValue(map, "items");
        assertNotNull(result);
        assertEquals(2, result.size());
    }

    @Test
    public void test_getListValue_notList() {

        Assertions.assertEquals(expected, actual, message);
    }

    // assertEquals - JUnit 4 style (message first) - int version
    protected void assertEquals(String message, int expected, int actual) {
        Assertions.assertEquals(expected, actual, message);
    }

    // assertSame - JUnit 5 style (no message)
    protected void assertSame(Object expected, Object actual) {

    private final Object[] cellValues;
    private final int[] cellRowIndices;
    private final int[] cellColumnIndices;

    private SerializedForm(
        Object[] rowKeys,
        Object[] columnKeys,
        Object[] cellValues,
        int[] cellRowIndices,
        int[] cellColumnIndices) {
      this.rowKeys = rowKeys;
      this.columnKeys = columnKeys;
      this.cellValues = cellValues;

    return comparator.compare(a, b);
  }

  @Override
  public boolean equals(@Nullable Object object) {
    if (object == this) {
      return true;
    }
    if (object instanceof ComparatorOrdering) {
      ComparatorOrdering<?> that = (ComparatorOrdering<?>) object;
      return this.comparator.equals(that.comparator);
    }
    return false;
  }

  @Override

        Map<Object, Object> map = new HashMap<Object, Object>();
        assertEquals(0, (int) StreamUtil.stream(map).get(s -> s.toArray().length));
    }

    public void test_ofMap() {
        Map<String, String> map = new HashMap<String, String>();
        map.put("key1", "value1");
        map.put("key2", "value2");
        StreamUtil.stream(map).of(s -> s.forEach(m -> assertEquals(map.get(m.getKey()), m.getValue())));
    }

    }

    @Input
    public Map<String, Object> getHostEnv() {
        return hostEnv.get();
    }

    public void hostEnv(String name, Object value) {
        hostEnv.put(name, value);
    }

    @Input
    public Map<String, Object> getVmEnv() {
        return vmEnv.get();
    }

    public void vmEnv(String name, Object value) {
        vmEnv.put(name, value);
    }

    @Input

    /**
     * Returns {@literal true} if the object is an array. Returns {@literal false} if the object is {@literal null}.
     *
     * @param object
     *            the object
     * @return {@literal true} if the object is an array; {@literal false} if the object is {@literal null}
     */
    public static boolean isArray(final Object object) {
        return object != null && object.getClass().isArray();
    }

  }

  /**
   * A sensible definition of {@link #subMultiset(Object, BoundType, Object, BoundType)} in terms of
   * {@link #headMultiset(Object, BoundType) headMultiset} and {@link #tailMultiset(Object,
   * BoundType) tailMultiset}.
   *
   * <p>If you override either of these methods, you may wish to override {@link
   * #subMultiset(Object, BoundType, Object, BoundType)} to forward to this implementation.
   */

        // Test with supported document type
        Map<String, Object> docMap = new HashMap<>();
        docMap.put("mimetype", "application/pdf");
        assertTrue(thumbnailGenerator.isTarget(docMap));
    }

    @Test
    public void test_isTarget_withUnsupportedMimeType() {
        // Test with unsupported document type
        Map<String, Object> docMap = new HashMap<>();