code: func (txops txOps) applyKVWrite(ns, coll string, kvWrite *kvrwset.KVWrite) {
  	if kvWrite.IsDelete {
  		txops.delete(compositeKey{ns, coll, kvWrite.Key})
  	} else {
  		txops.upsert(compositeKey{ns, coll, kvWrite.Key}, kvWrite.Value)
  	}
  }
docs: // applyKVWrite records upsertion/deletion of a kvwrite