code: function serializeTopics(topics) {
      return topics.map(function (topic) {
          if (typeof (topic) === 'string') {
              return topic;
          }
          else if (Array.isArray(topic)) {
              topic.forEach(function (topic) {
                  if (topic !== null && bytes_1.hexDataLength(topic) !== 32) {
                      errors.throwError('invalid topic', errors.INVALID_ARGUMENT, { argument: 'topic', value: topic });
                  }
              });
              return topic.join(',');
          }
          else if (topic === null) {
              return '';
          }
          return errors.throwError('invalid topic value', errors.INVALID_ARGUMENT, { argument: 'topic', value: topic });
      }).join('&');
  }
docs: //////////////////////////// Event Serializeing