code: public KafkaClient setProducerProperties(Properties props) {
          if (props == null) {
              producerProperties = null;
          } else {
              producerProperties = new Properties();
              producerProperties.putAll(props);
          }
          return this;
      }
docs: Sets custom producer configuration properties.
  
  @param props
  @return
  @since 1.2.1