docs: def _get(self, msgid):
          """Yields the message header against each part from the message."""
          foldername, msgkey = msgid.split(SEPERATOR)
          folder = self.folder if foldername == "INBOX" else self._getfolder(foldername)
          # Now look up the message
          msg = folder[msgkey]
          msg.is_seen = True
          hdr = list(msg.items())
          for p in msg.walk():
              yield hdr,p
          return