return requested attribute value as (namespace,name) or None

def getAttributeQName(self, attribute):
        """return requested attribute value as (namespace,name) or None 
        """
        qname = self.getAttribute(attribute)
        if isinstance(qname, TypeDescriptionComponent) is True:
            return qname
        if qname is None:
            return None

        prefix,ncname = SplitQName(qname)
        namespace = self.getXMLNS(prefix)
        return TypeDescriptionComponent((namespace,ncname))