def iterate(self, index, step, n_cols=70):
        """
        Return an iterator that starts and the current index and increments
        by the given step.
        """

        while True:
            if step < 0 and index < 0:
                # Hack to prevent displaying a submission's post if iterating
                # comments in the negative direction
                break
            try:
                yield self.get(index, n_cols=n_cols)
            except IndexError:
                break
            index += step

        Return an iterator that starts and the current index and increments
        by the given step.
        
rtv/content.py