docs: static void writeOrigin(DataOutput out, SimpleConfigOrigin origin,
              SimpleConfigOrigin baseOrigin) throws IOException {
          Map<SerializedField, Object> m;
          // to serialize a null origin, we write out no fields at all
          if (origin != null)
              m = origin.toFieldsDelta(baseOrigin);
          else
              m = Collections.emptyMap();
          for (Map.Entry<SerializedField, Object> e : m.entrySet()) {
              FieldOut field = new FieldOut(e.getKey());
              Object v = e.getValue();
              writeOriginField(field.data, field.code, v);
              writeField(out, field);
          }
          writeEndMarker(out);
      }