code: def unblockUser(self, user_id):
          
          data = {"fbid": user_id}
          r = self._post(self.req_url.UNBLOCK_USER, data)
          return r.ok
docs: Unblocks messages from a blocked user
  
          :param user_id: The ID of the user that you want to unblock
          :return: Whether the request was successful
          :raises: FBchatException if request failed