code: def parseExternalSubset(self, ExternalID, SystemID):
          
          libxml2mod.xmlParseExternalSubset(self._o, ExternalID, SystemID)
docs: parse Markup declarations from an external subset  [30]
            extSubset ::= textDecl? extSubsetDecl  [31] extSubsetDecl
             ::= (markupdecl | conditionalSect | PEReference | S) *