<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def on_key_up(self):
 """ Process key up event by updating buffer and release key. """

        if (self.last_pressed is not None):
            self.set_key_state(self.last_pressed, 0)
            self.buffer = self.last_pressed.update_buffer(self.buffer)
            self.text_consumer(self.buffer)
            self.last_pressed = None