code: def newDtd(self, name, ExternalID, SystemID):
          
          ret = libxml2mod.xmlNewDtd(self._o, name, ExternalID, SystemID)
          if ret is None:raise treeError('xmlNewDtd() failed')
          __tmp = xmlDtd(_obj=ret)
          return __tmp
docs: Creation of a new DTD for the external subset. To create an
             internal subset, use xmlCreateIntSubset().