def run_step(self):
        """Write in to out, replacing strings per the replace_pairs."""
        formatted_replacements = self.context.get_formatted_iterable(
            self.replace_pairs)

        iter = StreamReplacePairsRewriterStep.iter_replace_strings(
            formatted_replacements)
        rewriter = StreamRewriter(iter)
        super().run_step(rewriter)
Write in to out, replacing strings per the replace_pairs.