demo not runnin

Listening... Press Ctrl+C to exit
Traceback (most recent call last):
  File "demo.py", line 27, in <module>
    detector.start(detected_callback=snowboydecoder.ding_callback,
AttributeError: 'module' object has no attribute 'ding_callback'


I get this error when running demo

i could record and play back my voice, so the microphone is correctlyconfigured

help!!