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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def init_progress_bar(self):
 """Initialize and return a progress bar."""

        # Forked worker processes can't show progress bars.
        disable = MapReduce._forked or not config.PROGRESS_BARS

        # Don't materialize iterable unless we have to: huge iterables
        # (e.g. of `KCuts`) eat memory.
        if disable:
            total = None
        else:
            self.iterable = list(self.iterable)
            total = len(self.iterable)

        return tqdm(total=total, disable=disable, leave=False,
                    desc=self.description)