Detect whether the element is HTML tag or not.

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

def _parseIsTag(self):
        """
        Detect whether the element is HTML tag or not.

        Result is saved to the :attr:`_istag` property.
        """
        el = self._element
        self._istag = el and el[0] == "<" and el[-1] == ">"