code: func (p PvtUpdateBatch) ToCompositeKeyMap() PvtdataCompositeKeyMap {
  	m := make(PvtdataCompositeKeyMap)
  	for ns, nsBatch := range p.UpdateMap {
  		for _, coll := range nsBatch.GetCollectionNames() {
  			for key, vv := range nsBatch.GetUpdates(coll) {
  				m[PvtdataCompositeKey{ns, coll, key}] = vv
  			}
  		}
  	}
  	return m
  }
docs: // ToCompositeKeyMap rearranges the update batch data in the form of a single map