@Override
  public void toDelta(DataOutput out) throws IOException {
    if (attributes instanceof Delta) {
      ((Delta) attributes).toDelta(out);
    } else {
      toData(out);
    }
  }
These three methods handle delta propagation and are deferred to the attribute object.
extensions/geode-modules-session-internal/src/main/java/org/apache/geode/modules/session/internal/filter/GemfireHttpSession.java