@Override
  public void fromDelta(DataInput in) throws IOException, InvalidDeltaException {
    if (attributes instanceof Delta) {
      ((Delta) attributes).fromDelta(in);
    } else {
      try {
        fromData(in);
      } catch (ClassNotFoundException cex) {
        throw new IOException("Unable to forward fromDelta() call " + "to fromData()", cex);
      }
    }
  }
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