def at_css(self, css, timeout = DEFAULT_AT_TIMEOUT, **kw):
    """ Returns the first node matching the given CSSv3 expression or ``None``
    if a timeout occurs. """
    return self.wait_for_safe(lambda: super(WaitMixin, self).at_css(css),
                              timeout = timeout,
                              **kw)
Returns the first node matching the given CSSv3 expression or ``None``
    if a timeout occurs.