docs: static UnionImpl fastWrap(final WritableMemory srcMem, final long seed) {
      Family.UNION.checkFamilyID(extractFamilyID(srcMem));
      final UpdateSketch gadget = DirectQuickSelectSketch.fastWritableWrap(srcMem, seed);
      final UnionImpl unionImpl = new UnionImpl(gadget, seed);
      unionImpl.unionThetaLong_ = extractUnionThetaLong(srcMem);
      unionImpl.unionEmpty_ = PreambleUtil.isEmpty(srcMem);
      return unionImpl;
    }