pub trait BeforeUnloadEventMethods<D>where
    D: DomTypes,{
    // Required methods
    fn ReturnValue(&self) -> DOMString;
    fn SetReturnValue(&self, value: DOMString);
    fn IsTrusted(&self) -> bool;
}pub trait BeforeUnloadEventMethods<D>where
    D: DomTypes,{
    // Required methods
    fn ReturnValue(&self) -> DOMString;
    fn SetReturnValue(&self, value: DOMString);
    fn IsTrusted(&self) -> bool;
}