Search the DTD for the description of this attribute on
           this element.

def dtdAttrDesc(self, elem, name):
        """Search the DTD for the description of this attribute on
           this element. """
        ret = libxml2mod.xmlGetDtdAttrDesc(self._o, elem, name)
        if ret is None:raise treeError('xmlGetDtdAttrDesc() failed')
        __tmp = xmlAttribute(_obj=ret)
        return __tmp