code: def structured_iterator(failure_lines):
      
      summary = partial(failure_line_summary, TbplFormatter())
      for failure_line in failure_lines:
          repr_str = summary(failure_line)
          if repr_str:
              yield failure_line, repr_str
  
      while True:
          yield None, None
docs: Create FailureLine, Tbpl-formatted-string tuples.