code: def headers(self):
      
      headers = self.conn.issue_command("Headers")
      res = []
      for header in headers.split("\r"):
        key, value = header.split(": ", 1)
        for line in value.split("\n"):
          res.append((_normalize_header(key), line))
      return res
docs: Returns a list of the last HTTP response headers.
      Header keys are normalized to capitalized form, as in `User-Agent`.