returns object instance representing QName --> (namespace,name),
           or if does not exist return None.
           attribute -- an information item attribute, with a QName value.
           collection -- collection in parent Schema instance to search.

def getQNameAttribute(self, collection, attribute):
        """returns object instance representing QName --> (namespace,name),
           or if does not exist return None.
           attribute -- an information item attribute, with a QName value.
           collection -- collection in parent Schema instance to search.
        """
        tdc = self.getAttributeQName(attribute)
        if not tdc:
            return

        obj = self.getSchemaItem(collection, tdc.getTargetNamespace(), tdc.getName())
        if obj: 
            return obj

#        raise SchemaError, 'No schema item "%s" in collection %s' %(tdc, collection)
        return