docs: def _info(message):
      """Convenience function to log current span values.
      """
      span = values()
      _log.debug(message + ": {span} in trace {trace}. (Parent span: {parent}).".format(
          span=span.get(b3_span_id),
          trace=span.get(b3_trace_id),
          parent=span.get(b3_parent_span_id),
      ))