code: def run_step(self):
          
          formatted_replacements = self.context.get_formatted_iterable(
              self.replace_pairs)
  
          iter = StreamReplacePairsRewriterStep.iter_replace_strings(
              formatted_replacements)
          rewriter = StreamRewriter(iter)
          super().run_step(rewriter)
docs: Write in to out, replacing strings per the replace_pairs.