Return percentage of cloud coverage.

def cloud_percent(self):
        """Return percentage of cloud coverage."""
        image_content_qi = self._metadata.findtext(
            (
                """n1:Quality_Indicators_Info/Image_Content_QI/"""
                """CLOUDY_PIXEL_PERCENTAGE"""
            ),
            namespaces=self._nsmap)
        return float(image_content_qi)