code: func newBlock(seqNum uint64, previousHash []byte) *common.Block {
  	block := &common.Block{}
  	block.Header = &common.BlockHeader{}
  	block.Header.Number = seqNum
  	block.Header.PreviousHash = previousHash
  	block.Data = &common.BlockData{}
  
  	var metadataContents [][]byte
  	for i := 0; i < len(common.BlockMetadataIndex_name); i++ {
  		metadataContents = append(metadataContents, []byte{})
  	}
  	block.Metadata = &common.BlockMetadata{Metadata: metadataContents}
  
  	return block
  }
docs: // NewBlock construct a block with no data and no metadata.