docs: def reset(self):
          """ (re)set all instance attributes to default.
  
          Every attribute is set to ``None``, except :attr:`author`
          and :attr:`failures` which are set to ``[]``.
          """
  
          self.config = None
          self.html = None
          self.parsed_tree = None
          self.tidied = False
          self.next_page_link = None
          self.title = None
          self.author = set()
          self.language = None
          self.date = None
          self.body = None
          self.failures = set()
          self.success = False
  
          LOGGER.debug(u'Reset extractor instance to defaults/empty.')