code: @Override
      public Map<String, Object> toSource() {
          Map<String, Object> sourceMap = new HashMap<>();
          if (createdBy != null) {
              addFieldToSource(sourceMap, "createdBy", createdBy);
          }
          if (createdTime != null) {
              addFieldToSource(sourceMap, "createdTime", createdTime);
          }
          if (generator != null) {
              addFieldToSource(sourceMap, "generator", generator);
          }
          if (path != null) {
              addFieldToSource(sourceMap, "path", path);
          }
          if (target != null) {
              addFieldToSource(sourceMap, "target", target);
          }
          if (thumbnailId != null) {
              addFieldToSource(sourceMap, "thumbnail_id", thumbnailId);
          }
          return sourceMap;
      }
docs: ======