def snake(self, duration: float = <NUM_LIT>):
for button in BUTTONS:<EOL><INDENT>self.light_on(button)<EOL>time.sleep(duration)<EOL><DEDENT>for button in reversed(BUTTONS):<EOL><INDENT>self.light_off(button)<EOL>time.sleep(duration)<EOL><DEDENT>
Turn the button lights on then off in a snakelike sequence.
NOTE! Does not remember prior state of lights and will finish
with all lights off.
:param duration: The duration to hold each individual button.