Currently, there is no method to parse back the block.Data. This will be required to read the block though (#212).

Ideally, this would be implemented in a separate PR. The way this would work is to use the fact, that the shares are encoded with a length delimiter. So by reading the length from a share, we should be able to deduct the number of shares a Tx (messages / interm. state roots/ evidence) actually spans and merge the shares back together (if necessary).

ref: celestiaorg/celestia-specs#147