code: func InitBlockMetadata(block *cb.Block) {
  	if block.Metadata == nil {
  		block.Metadata = &cb.BlockMetadata{Metadata: [][]byte{{}, {}, {}}}
  	} else if len(block.Metadata.Metadata) < int(cb.BlockMetadataIndex_TRANSACTIONS_FILTER+1) {
  		for i := int(len(block.Metadata.Metadata)); i <= int(cb.BlockMetadataIndex_TRANSACTIONS_FILTER); i++ {
  			block.Metadata.Metadata = append(block.Metadata.Metadata, []byte{})
  		}
  	}
  }
docs: // InitBlockMetadata copies metadata from one block into another