Args:
            opener (obj): :class:`HTMLElement` instance.

        Returns:
            bool: True, if this element is endtag to `opener`.

def isEndTagTo(self, opener):
        """
        Args:
            opener (obj): :class:`HTMLElement` instance.

        Returns:
            bool: True, if this element is endtag to `opener`.
        """
        if not (self._isendtag and opener.isOpeningTag()):
            return False

        return self._tagname.lower() == opener.getTagName().lower()