.put(TimeUnit.class, SECONDS)
          .put(Charset.class, UTF_8)
          .put(Currency.class, Currency.getInstance(Locale.US))
          .put(Locale.class, Locale.US)
          .put(Optional.class, Optional.empty())
          .put(OptionalInt.class, OptionalInt.empty())
          .put(OptionalLong.class, OptionalLong.empty())
          .put(OptionalDouble.class, OptionalDouble.empty())

# OkHttp test platform rules uses optional classes.

import org.codelibs.fess.opensearch.config.exentity.ScheduledJob;
import org.codelibs.fess.util.ComponentUtil;
import org.codelibs.fess.util.RenderDataUtil;
import org.dbflute.optional.OptionalEntity;
import org.dbflute.optional.OptionalThing;
import org.lastaflute.web.Execute;
import org.lastaflute.web.response.HtmlResponse;
import org.lastaflute.web.response.render.RenderData;

    * `dict`의 키(key)는 `str`타입이다. (각 아이템의 이름(name))
    * `dict`의 값(value)는 `float`타입이다. (각 아이템의 가격(price))

#### `Optional`

`str`과 같이 타입을 선언할 때 `Optional`을 쓸 수도 있는데, "선택적(Optional)"이기때문에 `None`도 될 수 있습니다:

```Python hl_lines="1  4"
{!../../docs_src/python_types/tutorial009.py!}
```

`Optional[str]`을 `str` 대신 쓰게 되면, 특정 값이 실제로는 `None`이 될 수도 있는데 항상 `str`이라고 가정하는 상황에서 에디터가 에러를 찾게 도와줄 수 있습니다.

#### Generic(제네릭) 타입

import org.codelibs.fess.app.web.profile.ProfileAction;
import org.codelibs.fess.util.ComponentUtil;
import org.codelibs.fess.util.RenderDataUtil;
import org.dbflute.optional.OptionalEntity;
import org.dbflute.optional.OptionalThing;
import org.lastaflute.web.Execute;
import org.lastaflute.web.login.exception.LoginFailureException;
import org.lastaflute.web.response.HtmlResponse;

package com.google.common.io;

import com.google.caliper.BeforeExperiment;
import com.google.caliper.Benchmark;
import com.google.caliper.Param;
import com.google.caliper.api.VmOptions;
import com.google.common.base.Optional;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.charset.Charset;
import java.util.Random;
import org.jspecify.annotations.NullUnmarked;

/**

            setupListCondition(cb, labelTypePager);
        });

        // update pager
        BeanUtil.copyBeanToBean(labelTypeList, labelTypePager, option -> option.include(Constants.PAGER_CONVERSION_RULE));
        labelTypePager.setPageNumberList(labelTypeList.pageRange(op -> {
            op.rangeSize(fessConfig.getPagingPageRangeSizeAsInteger());
        }).createPageNumberList());

   *     in this instance of the Java virtual machine
   */
  public Optional<Charset> charset() {
    // racy single-check idiom, this is safe because Optional is immutable.
    Optional<Charset> local = parsedCharset;
    if (local == null) {
      String value = null;
      local = Optional.absent();
      for (String currentValue : parameters.get(CHARSET_ATTRIBUTE)) {
        if (value == null) {

        // As a side effect it will log the optional projects that could not be resolved.
        projectSelector.getOptionalProjectsBySelectors(request, session.getAllProjects(), allOptionalSelectors);
    }

    /**
     * Check whether any of the requested optional profiles were not activated or deactivated.
     * @param session the Maven session.
     * @param profileActivation the requested optional and required profiles.
     */

For example, this model above declares a JSON "`object`" (or Python `dict`) like:

```JSON
{
    "name": "Foo",
    "description": "An optional description",
    "price": 45.2,
    "tax": 3.5
}
```

...as `description` and `tax` are optional (with a default value of `None`), this JSON "`object`" would also be valid:

```JSON