/**
   * @throws IllegalArgumentException if {@code existingValue} is not null.
   */
  /*
   * We could have declared this method 'static' but the additional compile-time checks achieved by
   * referencing the type variables seem worthwhile.
   */
  final void checkNoDuplicate(R rowKey, C columnKey, @Nullable V existingValue, V newValue) {
    checkArgument(
        existingValue == null,

    }

    // Test getAsString with default value
    public void test_getAsStringWithDefaultValue() {
        dataStoreParams.put("existingKey", "existingValue");
        assertEquals("existingValue", dataStoreParams.getAsString("existingKey", "defaultValue"));

        assertNull(dataStoreParams.getAsString("nonExistentKey"));

  }

  @MapFeature.Require(absent = SUPPORTS_PUT)
  @CollectionSize.Require(absent = ZERO)
  public void testPut_unsupportedPresentExistingValue() {
    try {
      assertEquals("put(present, existingValue) should return present or throw", v0(), put(e0()));
    } catch (UnsupportedOperationException tolerated) {
    }
    expectUnchanged();
  }

  @MapFeature.Require(absent = SUPPORTS_PUT)

        // Test loading into existing map
        paramMap = new HashMap<>();
        paramMap.put("existing", "existingValue");
        configParam = "key1=value1\nkey2=value2";
        ParameterUtil.loadConfigParams(paramMap, configParam);
        assertEquals(3, paramMap.size());
        assertEquals("existingValue", paramMap.get("existing"));
        assertEquals("value1", paramMap.get("key1"));

  }

  @MapFeature.Require(absent = SUPPORTS_PUT)
  @CollectionSize.Require(absent = ZERO)
  public void testPut_unsupportedPresentExistingValue() {
    try {
      assertEquals("put(present, existingValue) should return present or throw", v0(), put(e0()));
    } catch (UnsupportedOperationException tolerated) {
    }
    expectUnchanged();
  }

  @MapFeature.Require(absent = SUPPORTS_PUT)