public Set<ValueAttribute> getUniqueAttributeBuilderAttributes() {
    if (uniqueNestedBuilderAttributes == null) {
      uniqueNestedBuilderAttributes = FluentIterable.from(getSettableAttributes())
          .filter(ValueAttributeFunctions.isAttributeBuilder())
          .filter(ValueAttributeFunctions.uniqueOnAttributeBuilderDescriptor())
          .toSet();
    }
    return uniqueNestedBuilderAttributes;
  }
Means object hashcode is cached at some point. Either lazily (on first access)
or eagerly (during construction).
@see #isUseLazyhash()
@see #isUsePrehashed()
value-processor/src/org/immutables/value/processor/meta/ValueType.java