sendKeys不工作并给出java.lang.charsequence错误

Question

下面是代码片段，当我尝试执行sendKeys时，它会抛出错误。

public class Revision {

    public static void main(String[] args) {

        WebDriver dr = new FirefoxDriver();

        dr.get("https://www.youtube.com/");

        dr.manage().window().maximize();

        dr.manage().timeouts().implicitlyWait(10, TimeUnit.SECONDS);

        WebElement you=dr.findElement(By.id("masthead-search-term"));

        you.sendKeys("lean on");