return key;
  }

  /**
   * Returns the current value for this system property by delegating to {@link
   * System#getProperty(String)}.
   *
   * <p>The value returned by this method is non-null except in rare circumstances:
   *
   * <ul>
   *   <li>{@link #JAVA_EXT_DIRS} was deprecated in Java 8 and removed in Java 9. We have not
   *       confirmed whether it is available under older versions.

    id: int
    name: str
    joined: date
```

Este puede ser usado como:

```Python
my_user: User = User(id=3, name="John Doe", joined="2018-07-19")

second_user_data = {
    "id": 4,
    "name": "Mary",
    "joined": "2018-11-30",
}

my_second_user: User = User(**second_user_data)
```

/// info | Información

`**second_user_data` significa:

  /**
   * Resets variables maintaining the sum to zero. This method may be a useful alternative to
   * creating a new adder, but is only effective if there are no concurrent updates. Because this
   * method is intrinsically racy, it should only be used when it is known that no threads are
   * concurrently updating.
   */
  public void reset() {
    internalReset(0L);
  }

  /**

  /**
   * Resets variables maintaining the sum to zero. This method may be a useful alternative to
   * creating a new adder, but is only effective if there are no concurrent updates. Because this
   * method is intrinsically racy, it should only be used when it is known that no threads are
   * concurrently updating.
   */
  public void reset() {
    internalReset(0L);
  }

  /**

	if !ok {
		dstRec = &Record{}
	}
	dstRec.object = v
	return dstRec, nil
}

// Close - closes underlying reader.
func (r *Reader) Close() error {
	// Close the input.
	// Potentially racy if the stream decoder is still reading.
	if r.readCloser != nil {
		r.readCloser.Close()
	}
	if r.exitReader != nil {
		close(r.exitReader)
		r.readerWg.Wait()
		r.exitReader = nil
		r.input = nil
	}

    cacheHit.cacheResponse()
      .assertCode(200)
      .assertHeader("Donut", "a")
      .assertHeader("ETag", "v1")
      .assertRequestUrl(server.url("/"))
      .assertRequestHeader("Accept-Language") // No Vary on Accept-Language.
      .assertRequestHeader("Accept-Charset", "UTF-8") // Because of Vary on Accept-Charset.

  /**
   * Resets variables maintaining the sum to zero. This method may be a useful alternative to
   * creating a new adder, but is only effective if there are no concurrent updates. Because this
   * method is intrinsically racy, it should only be used when it is known that no threads are
   * concurrently updating.
   */
  public void reset() {
    internalReset(0L);
  }

  /**

    List<String> list = Lists.newArrayList("mary", "bob");
    assertEquals(0, Iterables.indexOf(list, equalTo("mary")));
    assertEquals(1, Iterables.indexOf(list, equalTo("bob")));
    assertEquals(-1, Iterables.indexOf(list, equalTo("jack")));
  }

  public void testIndexOf_withDuplicates() {
    List<String> list = Lists.newArrayList("mary", "bob", "bob", "bob", "sam");

second_user_data = {
    "id": 4,
    "name": "Mary",
    "joined": "2018-11-30",
}

my_second_user: User = User(**second_user_data)
```

/// info

`**second_user_data` nghĩa là:

Truyền các khóa và giá trị của dict `second_user_data` trực tiếp như các tham số kiểu key-value, tương đương với: `User(id=4, name="Mary", joined="2018-11-30")`

///

### Được hỗ trợ từ các trình soạn thảo

my_user: User = User(id=3, name="John Doe", joined="2018-07-19")

second_user_data = {
    "id": 4,
    "name": "Mary",
    "joined": "2018-11-30",
}

my_second_user: User = User(**second_user_data)
```


/// info

`**second_user_data` 意思是:

直接将`second_user_data`字典的键和值直接作为key-value参数传递，等同于：`User(id=4, name="Mary", joined="2018-11-30")`

///

### 编辑器支持

整个框架都被设计得易于使用且直观，所有的决定都在开发之前就在多个编辑器上进行了测试，来确保最佳的开发体验。