@classmethod
def _progress_handler(cls, message, percentage):
    """Progress bar handler, called when C{igraph} reports the progress
        of an operation

        @param message: message provided by C{igraph}
        @param percentage: percentage provided by C{igraph}
        """
    if percentage >= 100:
        cls.progress_bar.clear()
    else:
        cls.progress_bar.update(percentage, message)
