DocMap docMap = new DocMap(parentMap);

        docMap.put("nullKey", null);
        assertTrue(docMap.containsKey("nullKey"));
        assertTrue(docMap.containsValue(null));
        assertNull(docMap.get("nullKey"));

        assertNull(docMap.put("nullKey", "newValue"));
        assertEquals("newValue", docMap.get("nullKey"));
    }

    @Test
    public void test_map_interface_compliance() {

    }

    // Test getAsString with null value
    @Test
    public void test_getAsStringWithNullValue() {
        dataStoreParams.put("nullKey", null);
        assertNull(dataStoreParams.getAsString("nullKey"));
    }

    // Test getAsString for non-existent key
    @Test
    public void test_getAsStringNonExistentKey() {
        assertNull(dataStoreParams.getAsString("nonexistent"));

  }

  public void testCopyOf_map_nulls() {
    Map<Class<? extends Number>, Number> nullKey = singletonMap(null, (Number) 1.0);
    assertThrows(NullPointerException.class, () -> ImmutableClassToInstanceMap.copyOf(nullKey));

    Map<? extends Class<? extends Number>, Number> nullValue = singletonMap(Number.class, null);

    List<@Nullable Integer> list5 = Lists.newArrayList(1, null, 2);
    List<@Nullable Integer> list6 = Lists.newArrayList(2);
    List<@Nullable Integer> list7 = Lists.newArrayList(nullInt);
    List<@Nullable Integer> list8 = Lists.newArrayList(nullInt, nullInt);
    List<@Nullable List<@Nullable Integer>> list =
        Lists.newArrayList(list1, list2, list3, list4, list5, list6, list7, list8, null);

    List<@Nullable Integer> list5 = Lists.newArrayList(1, null, 2);
    List<@Nullable Integer> list6 = Lists.newArrayList(2);
    List<@Nullable Integer> list7 = Lists.newArrayList(nullInt);
    List<@Nullable Integer> list8 = Lists.newArrayList(nullInt, nullInt);
    List<@Nullable List<@Nullable Integer>> list =
        Lists.newArrayList(list1, list2, list3, list4, list5, list6, list7, list8, null);

      boolean permitsDuplicates,
      @Nullable String nullKey,
      @Nullable Integer nullValue) {
    multimap.clear();
    multimap.put("foo", 1);
    multimap.put("foo", 2);
    multimap.put("foo", 3);
    multimap.put("bar", 5);
    multimap.put("bar", -1);
    multimap.put(nullKey, nullValue);
    multimap.put("foo", nullValue);
    multimap.put(nullKey, 5);
    multimap.put("foo", 2);

  }

  public void testOfEntriesNull() {
    Entry<@Nullable Integer, Integer> nullKey = entry(null, 23);
    assertThrows(
        NullPointerException.class,
        () -> ImmutableBiMap.ofEntries((Entry<Integer, Integer>) nullKey));
    Entry<Integer, @Nullable Integer> nullValue =
        ImmutableBiMapTest.<@Nullable Integer>entry(23, null);
    assertThrows(

        try {
            WebApiUtil.setObject("validKey", "validValue");
            WebApiUtil.setObject("", "emptyKey");
            WebApiUtil.setObject("nullValue", null);
            WebApiUtil.setObject(null, "nullKey");
            WebApiUtil.setObject(null, null);
        } catch (Exception e) {
            fail("setObject should handle parameter validation gracefully: " + e.getMessage());
        }

* Update Netlify previews deployment GitHub action as the fix is already merged and there's a new release. PR [#1047](https://github.com/tiangolo/fastapi/pull/1047).
* Move mypy configurations to config file. PR [#987](https://github.com/tiangolo/fastapi/pull/987) by [@hukkinj1](https://github.com/hukkinj1).