code: def _parse_tagfile(self):
          
          rules = None
          tag = None
          for line in self.original:
              match = self.TAG_DECL_LINE.match(line)
              if match:
                  if tag and rules:
                      yield tag, rules
                  rules = []
                  tag = match.group(1)
                  continue
  
              match = self.TAG_RULE_LINE.match(line)
              if match:
                  source = match.group(1)
                  rules.append(self._parse_query(source))
docs: Parse the tagfile and yield tuples of tag_name, list of rule ASTs.