code: func (b *RWSetBuilder) AddToHashedMetadataWriteSet(ns, coll, key string, metadata map[string][]byte) {
  	// pvt write set just need the key; not the entire metadata. The metadata is stored only
  	// by the hashed key. Pvt write-set need to know the key for handling a special case where only
  	// metadata is updated so, the version of the key present in the pvt data should be incremented
  	b.getOrCreateCollPvtRwBuilder(ns, coll).
  		metadataWriteMap[key] = &kvrwset.KVMetadataWrite{Key: key, Entries: nil}
  	b.getOrCreateCollHashedRwBuilder(ns, coll).
  		metadataWriteMap[key] = mapToMetadataWriteHash(key, metadata)
  }
docs: // AddToHashedMetadataWriteSet adds a metadata to a key in the hashed write-set