if (value instanceof Delta) {
// magic
Delta dv = (Delta) value;
DeltaAware toMergeWith = null;
if (entryValue instanceof DeltaAware) toMergeWith = (DeltaAware) entryValue;
e.setValue(dv.merge(toMergeWith));
o = entryValue;
e.setLifespan(lifespanMillis);
e.setMaxIdle(maxIdleTimeMillis);
} else {
o = e.setValue(value);