Return the enumeration member corresponding to the XML value
        *xml_val*.

def from_xml(cls, xml_val):
        """
        Return the enumeration member corresponding to the XML value
        *xml_val*.
        """
        if xml_val not in cls._xml_to_member:
            raise InvalidXmlError(
                "attribute value '%s' not valid for this type" % xml_val
            )
        return cls._xml_to_member[xml_val]