code: func (lc *LightChain) GetBlockByHash(ctx context.Context, hash common.Hash) (*types.Block, error) {
  	number := lc.hc.GetBlockNumber(hash)
  	if number == nil {
  		return nil, errors.New("unknown block")
  	}
  	return lc.GetBlock(ctx, hash, *number)
  }
docs: // GetBlockByHash retrieves a block from the database or ODR service by hash,
  // caching it if found.