docs: def _postrun(cls, span, obj, **kwargs):
          """ Trigger to execute just before closing the span
  
          :param opentracing.span.Span  span: the SpanContext instance
          :param Any obj: Object to use as context
          :param dict kwargs: additional data
          """
          for key, value in ResultSchema().dump(obj.result).items():
              if isinstance(value, dict):
                  try:
                      flat_data = cls.filter_keys(
                          cls.fix_additional_fields(value)
                      )
                      span.set_tag("result.{}".format(key), json.dumps(flat_data))
                  except Exception:
                      span.set_tag("result.{}".format(key), "N/A")
              elif isinstance(value, (list, tuple)):
                  try:
                      span.set_tag("result.{}".format(key), json.dumps(value))
                  except Exception:
                      try:
                          span.set_tag("result.{}".format(key), value)
                      except Exception:
                          span.set_tag("result.{}".format(key), "N/A")
              else:
                  span.set_tag("result.{}".format(key), value)