code: def addDocEntity(self, name, type, ExternalID, SystemID, content):
          
          ret = libxml2mod.xmlAddDocEntity(self._o, name, type, ExternalID, SystemID, content)
          if ret is None:raise treeError('xmlAddDocEntity() failed')
          __tmp = xmlEntity(_obj=ret)
          return __tmp
docs: Register a new entity for this document.