Property that checks if the specified window is private or not.

        Returns:
            bool: True if this is a Private Browsing window.

def is_private(self):
        """Property that checks if the specified window is private or not.

        Returns:
            bool: True if this is a Private Browsing window.

        """
        self.switch_to()
        with self.selenium.context(self.selenium.CONTEXT_CHROME):
            return self.selenium.execute_script(
                """
                Components.utils.import("resource://gre/modules/PrivateBrowsingUtils.jsm");

                let chromeWindow = arguments[0].ownerDocument.defaultView;
                return PrivateBrowsingUtils.isWindowPrivate(chromeWindow);
                """,
                self.document_element,
            )