Get element with ``wdom_id``.

def getElementByWdomId(id: str) -> Optional[WebEventTarget]:
    """Get element with ``wdom_id``."""
    if not id:
        return None
    elif id == 'document':
        return get_document()
    elif id == 'window':
        return get_document().defaultView
    elm = WdomElement._elements_with_wdom_id.get(id)
    return elm