code: public void setPartConverters(List<HttpMessageConverter> partConverters) {
          checkNotNull(partConverters, "'partConverters' must not be null");
          checkArgument(!partConverters.isEmpty(), "'partConverters' must not be empty");
          this.partConverters = partConverters;
      }
docs: Set the message body converters to use. These converters are used to
  convert objects to MIME parts.