docs: public DeferredValue<V> shallowCopy() {
          if (this == NULL_VALUE) {
              return NULL_VALUE;
          }
          DeferredValue<V> copy = new DeferredValue<V>();
          if (serializedValueExists) {
              copy.serializedValueExists = true;
              copy.serializedValue = serializedValue;
          }
          if (valueExists) {
              copy.valueExists = true;
              copy.value = value;
          }
          return copy;
      }