code: def message_callback_remove(self, sub):
          
          if sub is None:
              raise ValueError("sub must defined.")
  
          self._callback_mutex.acquire()
          for i in range(0, len(self.on_message_filtered)):
              if self.on_message_filtered[i][0] == sub:
                  self.on_message_filtered.pop(i)
                  self._callback_mutex.release()
                  return
          self._callback_mutex.release()
docs: Remove a message callback previously registered with
          message_callback_add().