def METHOD_NAME(self, volumeNode):
    """This is an example logic method that
    returns true if the passed in volume
    node has valid image data
    """
    if not volumeNode:
        logging.debug('hasImageData failed: no volume node')
        return False
    if volumeNode.GetImageData() is None:
        logging.debug('hasImageData failed: no image data in volume node')
        return False
    return True