Set digital pin 6 as a PWM output and set its output value to 128
    @param my_board: A PymataCore instance
    @return: No Return Value

async def pin_6_pwm_128(my_board):
    """
    Set digital pin 6 as a PWM output and set its output value to 128
    @param my_board: A PymataCore instance
    @return: No Return Value
    """
    # set the pin mode
    await my_board.set_pin_mode(6, Constants.PWM)

    # set the pin to 128
    await my_board.analog_write(6, 128)

    # let the led stay lit for 3 seconds
    await asyncio.sleep(3)

    # shutdown
    await my_board.shutdown()