Detect whether the element is HTML comment or not.

        Result is saved to the :attr:`_iscomment` property.

def _parseIsComment(self):
        """
        Detect whether the element is HTML comment or not.

        Result is saved to the :attr:`_iscomment` property.
        """
        self._iscomment = (
            self._element.startswith("<!--") and self._element.endswith("-->")
        )