Detect whether the element is nonpair or not (ends with ``/>``).

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

def _parseIsNonPairTag(self):
        """
        Detect whether the element is nonpair or not (ends with ``/>``).

        Result is saved to the :attr:`_isnonpairtag` property.
        """
        self._isnonpairtag = False

        if self._iscomment:
            return

        if self._element.startswith("<") and self._element.endswith("/>"):
            self._isnonpairtag = True

        # check listed nonpair tags
        if self._istag and self._tagname.lower() in NONPAIR_TAGS:
            self._isnonpairtag = True