async isDayFocused(day) {
        const buttonEl = await $(this.rootElement)
            .$('table')
            .$(`button=${day}`);
        // eslint-disable-next-line no-return-await
        return (await buttonEl.isExisting()) && (await buttonEl.isFocused());
    }
Returns true when the specific day button element has focus.
@method
@returns {bool}