code: func (l *kvLedger) GetPvtDataAndBlockByNum(blockNum uint64, filter ledger.PvtNsCollFilter) (*ledger.BlockAndPvtData, error) {
  	blockAndPvtdata, err := l.blockStore.GetPvtDataAndBlockByNum(blockNum, filter)
  	l.blockAPIsRWLock.RLock()
  	l.blockAPIsRWLock.RUnlock()
  	return blockAndPvtdata, err
  }
docs: // GetPvtDataAndBlockByNum returns the block and the corresponding pvt data.
  // The pvt data is filtered by the list of 'collections' supplied